There are plenty of nice Compiz themes at compiz.net. Here's Milk, which I've always liked. KDE + Compiz is just too nice:
Since taking these screenshots, I've started using dual monitors. There's a good FAQ on the Gentoo Wiki about setting up TwinView. It honestly couldn't be easier. I don't know how I got along with only one monitor before now. It's so much nicer with two.
The only bad thing about TwinView is that you can't specify which screen is your "main" screen. As seen in this thread, this is a limitation of the nvidia drivers. Kind of sucks, but KDE's support for dual screens makes up for nvidia's lack. You can force Kicker to be on one or the other screen or both; you can set wallpaper for each independently; etc. Full-screening most apps works fine. It all works perfectly fine with XGL/Compiz too.
Linux has come so far in the past 5 or 6 years. It's really quite amazing.