For static avatars, I just use Photoshop.
Marquee-->Crop-->Resize-->Save for Web.
To take a source from a fansub, open it in Virtual Dub, find the frame you want to use, and use the copy source Frame to Clipboard, and do as above.
To take a source from DVD, use frame capture, do as above.
gifs:
To make an animated gif, get your DVD source as you would for making an AMV, open the avs file in Vdub, select the range of frames you want to use, and then use File-->Save Image sequence to save all the frames you want to use, then crop, resize and animate using Image Ready, Photoshop's companion program.
For taking sequences from fansubs, do the second part as above:
Select the range of frames you want to use, and then use File-->Save Image sequence to save all the frames you want to use, then crop, resize and animate using Image Ready, Photoshop's companion program.
I know Photoshop is $$$, but maybe you can get a student discount.
Woo! I've got my drunk on tonight!

My Eyes Are The Victim's Eyes.
My Hands Are The Assailant's Hands.