You don't need any browser add-ons or programs like flashget to keep those flash games and music/funny/whatever videos you like from places such as youtube and newgrounds. All you need is your browser and windows explorer.
Let me get this tip out of the way before I start. A great tool for playing flash animations, games and videos on your hard drive is available free from the adobe site( http://www.adobe.com/support/flashplayer/downloads.html ).
Scroll down until you see a link called "Download the Windows Flash Player 9 Projector content debugger (EXE, 2.68 MB)".
It should go without saying that Mac and Linux users should download the version for their respective operating systems but I'm saying it anyway.
Stuff you need to know first:
Since this tutorial involves hidden folders (local settings & application data) and file extensions (you'll need to edit them later) you'll need to know how to see those:
Open control panel and double click "folder options"
In the folder options dialog that just opened select the "view" tab
Put a dot next to "show hidden files and folders" and untick "hide extensions for known file types" as shown in the pic and hit apply.
You'll also need to know the location of your browser's cache folder so here's where you'll find some of those:
Firefox 2.x.x.x - C:\Documents and Settings\[Your user name]\Local Settings\Application Data\Mozilla\Firefox\profiles\[something].default\cache\
Opera 9.xx - C:\Documents and Settings\[Your user name]\Application Data\Opera\Opera\Profile\cache4
IE7 - Dont know, I don't use it.
I (and hotdogsrgross) find that Opera is the best browser to use for this since it leaves the file extension alone and doesn't rename the flash files beyond recognition (ie: [jumbled numbers and stuff].tmp).
Find yourself a flash game or video you want, start it playing and wait until it fully buffers.
Leave your browser open and locate it's cache folder. Sort this folder by file size (right click>arrange icons by>size).
Copy the largest file and paste it to your desktop. Be aware that if it's only a short video the file you are looking for may not be the biggest in the cache.
Right click the file, select rename and add .swf or .flv to the end of the file's name and hit return/enter. I've used both .swf and .flv on flash games and it doesn't seem to matter which you choose, the debug player runs it anyway.
A) Open the file with the debug player from the Adobe link at the top of this post.
B) Double click the file. It'll probably open in your browser anyway.
C) Open it in VLC player, but only if it's a video, games won't work in VLC.