I thought Miranda Cosgrove was really funny in Drake and Josh (in before hurr you're a FAG), not so much iCarly, so I wasn't expecting much from her as a singer, but wow... I'm addicted as fuck to "Headphones On", which was released as RB2 DLC free. Its got a catchy tune and great matching vocal pitches. The lyrics, not much to say on that due to it being for kids.
I originally got "I Don't Wanna Goto School" by the Naked Brothers Band as a joke; because I used to always make fun of that song, but on Rock Band 2? Fucking fun time you can play over and over again. It will probably be considered a joke song to most pubescent people who download it, BUT at least in my opinion, it'll be somewhat catchy unlike that retarded Stephen Colbert song.
I also bought the other NBB song which was like "Body I Occupy", which is my least favorite of the three, but still a pretty decent song.
For those of you who are going to say "hurr you're just trying to be different" go fly a donut, dumpfist. Seriously, I came in expecting just God-awful songs and I find myself replay each song multiple times; overall, it was a very good buy.
Both NBB songs cost only 80 MSP, which is 99 cents. Once again the MC song is free.
Also, my friend made an awesome game called "Swords and Monsters" for Community Games on 360.
Here's the free demo: http://marketplace.xbox.com/en-US/games/media/66acd000-77fe-1000-9115-d80258550130/?gu=66acd000-77fe-1000-9115-d80258550130&sb=1&mt=32&p=1&of=0