There's an RPi category on Distrowatch: link
The Raspberry Pi Foundation also offers NOOBS for an easier installation. Two of the available options are Arch and Pidora (Fedora).
There's also the eLinux RPi Hub, which lists available distros here, and has tons and tons of other info.
If you have some experience with linux, I'd definitely recommend Arch. If you don't, Raspbian or PiDora via NOOBS is probably your best bet.
There's a lot of websites about how to install other distros. If you know which one you want, google it. :)
Every distro is capable of running python, browsers, and servers, so don't worry about that part. :)
Personally, I'm running a server on Raspbian (nginx + sqlite + php), and haven't had problems. Then again, I never use the GUI.
If you're only logging in via the GUI, you should run
raspi-config and reserve more memory for the video card. You can also overclock the RPi without losing your warranty via
raspi-config. Finally, if you've been using the default browser, Midori, there's a lot of lighter options.