Just got my RPi, what should I do first?

To start with I need an OS. Is installing an OS on an SD card the same as a flash drive? Also, which distros do I have to choose from? And lastly, what are some good websites/forums related to RPi projects?

I've been planning to get a raspberry pi recently. I've been hanging around this forum:  

http://www.raspberrypi.org/forum/

Aside from this, I can't help very much. Sorry. 

A couple things come to find

http://lifehacker.com/5929913/build-a-xbmc-media-center-with-a-35-raspberry-pi/all

And for what I'm planning to my first one as that I got today

http://lifehacker.com/how-to-turn-your-raspberry-pi-into-a-retro-game-console-498561192

The Raspberry Pi forum is probably the best way to go about finding information and things to do though