You can do an awful lot of very clever things with a Raspberry Pi, many of which we've covered here at Lifehacker previously. But if the prospect of setting up SD cards and choosing a distribution is just a bit too daunting, a new tool should make it a much more inviting prospect.
NOOBS -- that's New Out Of Box Software -- is a utility designed to make setting up a Pi for the first time substantially easier. No messing around with shifting images or anything of the sort.
You simply download the NOOBS ZIP file, unzip it onto a 4GB or larger SD card and pop it into the Pi. Boot it up, and it will hit you with a menu where you can choose your distribution of choice to install, be it the near-default Raspbian or something more media-centric such as RaspBMC. NOOBS stays resident on the card, which means if you ever fancy switching operating systems, it's as simple as holding shift down during the boot sequence.