Most popular songs are also fairly easy to play, especially in the blues or rock genres. There's a bunch of free guitar lessons on the internet so if you have a list of favorites songs I'd suggest typing them into a search engine together with the words 'free tabs' or 'free chord charts'. Also, as the saying goes, don't forget the lyrics, you can usually get those for free, too.

I've gone around to a few websites to see what songs were considered both popular and easy, and there really is quite a large range out there for a beginner guitarist with half an hour a day to practice and some enthusiasm for learning to play some songs. Here's a few I've found: About A Girl By Nirvan