• Firefox Portable: Data/plugins
• Opera USB: program/plugins
• Iron Portable: Iron/plugins
• Chrome Portable: get Iron you freak! :p

Note that this is not an official release from Adobe, it’s a custom, “home-made” package.
Also, note that Flash is not 100% portable: some sites will leave Local Shared Objects (LSO) on the computer where you use it. To remove them, you can either use the BetterPrivacy Firefox extension or Adobe’s Global Storage Settings panel (to disable future storing of LSOs) and Adobe’s Website Storage Settings panel (to delete already stored LSOs).

Flash 10.1 final for portable browsers

If you don’t want to grab 7-Zip portable, here are the same Flash files but in a ZIP archive.

As requested in a comment, here are the SHA 512 checksums:
SHA512 of file: NPSWF32.dll
dcdf4dccb5359a36 607a85c3034ef6f0 7a3597c0af00d42f bebee5c12af534fa
39ff83f8a3bc9f15 802cb3d18a138d44 41292b8f9032e758 73ef55d530ea1400

SHA512 of file: flashplayer.xpt
494146bb31cf0e11 5a6e1c632a8ed560 8046f5a8b2bbc900 832befb07b8f1425
81483c222067e440 5fc2755b5acf722d 576ac04b2b6d9f79 6e5a872fd5c7ddc9

A couple of weeks ago I posted about installing Flash on portable Firefox, Opera and Iron. By that time I was too lazy to mirror the necessary files myself and pointed you to third-party websites to grab the ready-to-unpack Flash files. Well, I recently tried the sixth release candidate of Flash 10.1, and couldn’t find a portable-ready version, so this time I uploaded mine.
Here it is: Flash 10.1 RC6 – NPSWF32.dll + flashplayer.xpt.

The instructions to use this are the same as with the previous versions (see for Firefox Portable / Opera-USB or Chrome and Iron Portable).
You can always find the latest Flash prerelease version at Adobe Labs (not portable-ready as far as Windows is concerned – the Linux version is portable).

Update: Flash 10.1 RC 7

The seventh release candidate was published today. Here’s the portable version of it: Flash 10.1 RC7 – NPSWF32.dll + flashplayer.xpt. It will test as version 10,1,53,64.
On a side note, as of version 10.1 Flash installs itself in C:\WINDOWS\system32\Macromed\Flash (at least in Windows XP).

Anyway, I decided that since this one is Google-free I could give it a go and add it to my portable software arsenal. And as with the portable Firefox and Opera the Flash player issue came up. The new problem? The plug-in folder was nowhere to be found. I eventually tried my luck and put it in the Iron root folder and… it worked. So, the steps to install Flash on Iron portable are:

• Create a folder called plugins in Iron root folder (so, Iron/plugins) (if you need more pointers this means that the plugins folder is at the same level as the extensions folder – Iron/extensions).
• Get a copy of NPSWF32.dll and flashplayer.xpt (see the guide for Firefox portable)
• Place those in the plugins folder
• Restart Iron

For Chrome portable (if for some reason you insist on getting that one), the process should be the same (I didn’t check it).

Update (June 1): you can also grab Flash 10.1 RC6 there.
Update (June 12): you can grab Flash 10.1 final here.

Firefox Portable, published by PortableApps.com, is a version of Firefox specially designed to be run from the folder where it is, without requiring an installation. This means that it can be used without administrative privileges and from a removable media like a USB key. So in More tips to freedom on a restricted computer environment I presented it as the way to install Firefox on a restricted computer. Opera-USB is the equivalent thing for Opera (except that since Opera isn’t free software it wasn’t made portable by PortableApps).
Leaving aside the connection configuration issues that were dealt with in the above-mentioned post, there is another problem with restricted computers: you can’t install plugins like Flash or Java. I didn’t study the Java case yet. But as for Flash, Firefox will use the installed Flash player if: 1. there is one and 2. the one installed is the generic version (i.e., multibrowser) and not the MSIE-only version. Which means that on a classic restricted computer happily limited to MSIE 6, Firefox Portable will most likely not be able to use the installed Flash player.
I found 2 ways to solve this problem:

Solution 1: the XPI

Adobe published a special version for Firefox, which is supposed to install like any other extension (aka now add-on). It turns out that the XPI fails to install. But, you can download it manually (for this you’ll need to right-click the following link and choose “save as”: http://fpdownload.adobe.com/get/flashplayer/xpi/current/flashplayer-win.xpi), unpack it (with any archiver supporting zip, i.e. you can do it with Windows if you change the file extension from .xpi to .zip), grab flashplayer.xpt and NPSWF32.dll and place them into the plug-in folder of Firefox Portable (in Data/plugins). Restart Firefox and voilà. For Opera-USB, the plug-in folder is program/plugins.
This method works and is quick and easy. The only problem is: Adobe doesn’t seem to update their XPI as often as they update the executable installer. This results in an outdated and thus insecure plug-in. As I’m writing, the version of the XPI is 10.0.32.18 (17 July 2009) while the current version is 10.0.45.2.

Solution 2: hacking the exe

Thanks to an article on eHow, I found this promising software called Universal Extractor (NB: it exists in a portable version). This free program, released under the GNU GPL v2, was designed to extract files from any type of archive or installer. It was suggested on eHow to use it to manually unpack the Flash installer, then grab the files as mentioned above about the XPI. Thus I downloaded the generic installer here (direct link), but when I tried to extract it with Universal Extractor it failed. I tried my luck with a 10.1 release candidate (RC4) from Adobe Labs, but it was not much better (it succeeding in extracting the files, but they all had strange names thus I couldn’t find the proper files, plus I thought they might be damaged anyway).
So, this leaves me with only two choices: grab the files from my home installation or grab the files from a site I consider safe to trust. For now I chose the second option. I came across a blog hosted by Opera Community, Tamil. They posted an up-to-date version of NPSWF32.dll. For Opera-USB, this is enough. For Firefox Portable, use this file along with flashplayer.xpt from the XPI. Restart your browser, then check your Flash installation.

Edit: at my home Flash installation, the Flash files (version 10.0.45.2) from my Opera plugins folder have the following MD5 checksums:
NPSWF32.dll: f8efdcfc440a420d6c1ecd245ab20207 (size: 3884312 bytes)
flashplayer.xpt: a81fd3b03b8c6d6e5a14298110718d3f (size: 856 bytes)
I compared NPSWF32.dll’s checksum to the one at Tamil’s, it’s the same.

Sources and versions

While dealing with this $#!t I found the following more or less useful pages

• Install Flash Plugin Manually in Firefox on Vista on How-To Geek
• How to Install Flash Player on Firefox Portable on eHow.com
• Flash version checker on Adobe.com: I already posted about it, but it’s so useful that it never hurts to remind it sometimes.
• Tamil – How to install flash player without administrator privilege for Opera?
• Hash functions on FileFormat.info: this page lets you calculate the most common checksums for a string or a file (md2, md4, md5, sha1, sha256, sha512…)

I did those things to Firefox Portable 3.6.3 and Opera@USB 10.53 on Windows XP SP2. The Flash versions I tried were 10.0.32.18, 10.0.45.2 and 10.1rc4. No registry key was hurt in the process, no CPU burnt and no hard drive failed despite the massive use of swap due to the ludicrous 512 MiB of installed RAM.

Quick guide (updated for Flash 10.1)

1. download NPSWF32.dll and flashplayer.xpt
2. save those files in Data/plugins (Firefox) or program/plugins (Opera)
3. restart your browser, and optionally check your installation.

Update (June 1): you can also grab Flash 10.1 RC6 there.
Update (June 12): you can grab Flash 10.1 final here.

Installing Flash for Firefox on Linux 64 bits is easy, but it’s a bit boring because since it’s still in alpha stage, there is no automated process to do it.
The manual steps are detailed here: https://fedoraproject.org/wiki/Flash#64-bit_alpha
In order to ease the pain, I eventually decided to make a tiny bash script that does this work for you. All you have to do, though, is to find the latest version number here on Adobe Labs (at the bottom of the page) and edit the script to set the proper version number (second line). Here’s the script (I hope WordPress doesn’t kill the quotes like it likes to do…), just copy/paste it, edit the version if needed and save as an .sh file that you’ll chmod to 744 and run:

#!/bin/bash
VERSION=10.0.45.2

echo "Finished"
echo "It should work even if Firefox was running, without restarting it."

This script was tested (and worked) on:

• Ubuntu 9.10 x64
• Ubuntu 10.04 x64
• Fedora 13 x64

Edit (28 June): other source (in French): http://doc.fedora-fr.org/wiki/Flash_:_Installation_du_plug-in
Edit (11 July): updated tested Linux versions.