High-quality videos with stereo sound on YoutubeTools used:
FRAPS 2.9.4
Windows Movie Maker (Vista/XP)
VMuTube Beta v1.0
http://gizm.brutix.com/VMuTube_BETA_v1.0.rarHow/why this works:
Youtube accepts videos with a filesize of up to 1024mb, a length of less than 11 minutes and an
average bitsize of 349kbit/sec. This is what we "abuse" in this tutorial. By adding blackness to the end of the video we can have a higher bitrate in the moving parts, and even stereo sound with up to 128kbps!

My Audiosurf settings for recording. Gives me a constant 60fps and keeps the .avi filesize somewhat small.

FRAPS 2.9.4 settings
Start Windows Movie Maker (WMM), and drag the video(s) you want to upload to Youtube on the program.

Drag the clip into the timeline. Press the (-) zoom out and click "Titles and Credits" on the left side of the screen.

"Credits at the end" is what you want to click here.

Enter anything you want. Click "Change the text font and color"

Doesn't matter which font. Text color black, background black, 90% transparency. Click "Add title"

Hooray, we've added blackness! Now click the right border of the credits and drag them so that the total playtime is almost 11 minutes.

Like so. Click File, Publish Movie, then choose This Computer, and name the movie "original". You should probably save it directly in your VMuTube folder.

Select "Compress to", and make the size as big as possible. You can switch to KB to make it a bit bigger still. Click publish.
Now we wait. Takes about 10 minutes on my system. Go pet your cat. Or maybe paint your room pink.

Hooray! Close WMM, locate your video file. If necessary, copy it to your VMuTube folder.
Double-click VMuTube.bat.

These settings give you the best possible result, but only really work with shorter songs (~3 minutes). 320x240 is for longer ones. Play around with them, sometimes 20 fps is enough and you get better video quality for slower songs.
What happens now is: audio is extracted to wav, converted to mp3, video converted to h263, resized to whatever you specified, audio and video added back together.

Done! final.flv should be somewhere 22-27mb. Upload the .flv to Youtube, impress your friends, family, teachers!
Here's two examples:
Tweaker's Doom 3 theme, self-made .flv, max settings:
http://www.youtube.com/watch?v=rrI3WmS_DbkTweaker's Doom 3 theme, Youtube .flv, uploaded the .wmv:
http://www.youtube.com/watch?v=pjnJ9f1IlHQAnd a longer song, not quite as drastic but still noticeable (mostly sound quality and red parts):
Pendulum - Blood Sugar, self-made .flv, sound 96, video 448x336:
http://www.youtube.com/watch?v=u9StwBZsmScPendulum - Blood sugar, Youtube .flv, uploaded the .wmv:
http://www.youtube.com/watch?v=n96ukoG1-kQ