XASEY SizeUp is great, filling a need I didn't know I had. Now I use it religiously... every time I open a new window. I like having a 20px margin around everything so my desktop shows through, and I have SizeUp set up to use the right third of the screen for small apps, then the left two-thirds for large windowed apps... and everything looks so nice and tidy. I find I often surf with two Safari windows open now, I'll pop open a video and hit the keys to make SizeUp shove that into the top of the screen, then I'll surf in another window on the bottom, then when the video is over I can hit a few keys and my surfing window goes right back to where it was to begin with. Same thing works great for having ftp and several finder windows open at the same time... it just looks so much nicer and is easier to work with.
Also, I mentioned to the developer that it would be cool if the feature that lets you move windows to other spaces could also do so by pressing a modifier and the number of the space you want, and he sent me a beta version and some applescripts that let me do just that! A quick key press now sends my todo list back and forth to to the space that has the app I'm working with at the time, and it ends up right in the gap to the side of the app. No dragging things around to make several things visible all at once. Cool!
(Version 1.2)