It's a... music community, for lack of shorter inclusive phrase. Bands can host, publicize, stream, etc. their creative-commons-licensed music, listeners can remix, playlist, rate, download, etc. them... artists can get revenue through donations and advertising, and the project aims to put musicians back out in front of their audience (instead of stuck in recording studios in order to make money).
Are you creative? Do you want your music to be listened to by a wider audience? jamendo brings the artists back on stage. Music is done by artists for the public and now is the time to get rid of exclusive intermediaries.
Their business model is fantastic. Seriously, it's like YouTube for music, but... open. My (occasional) band, License Server is recording a song just so we can put it on Jamendo. It's that cool.
As if that weren't enough, they're also partnering with OLPC. I was lucky enough to be able to meet Sylvain, the CTO and founder of Jamendo, at Wikimania this year. (And when I say "amazing," I mean "we had a single conversation one evening and by the following day he appeared with a music collection bundled for the laptop and scripts to autogenerate more, along with a press release for recruiting more Jamendo musicians.")
So... yeah. Go! Find yourselves some great music! (Oh - did I mention it's multilingual and multicultural, and that Peruvian pop and Indian rock sound really good?) Better yet, make some music, CC-license it, and share it on Jamendo. And if you put "OLPC" before the name of a playlist you're making, it'll automatically add it to the OLPC library.