Most AC/DC songs are easy and will give you good practice with simple chords. Take your pick, really. Someone wisely mentioned Back in Black. I'd also add TNT, Dirty Deeds..., Shake A Leg and Livewire as particularly straightforward.
Old Scorpions songs are good power chord practice. Rock You Like A Hurricane and their cover of the Who song I Can't Explain fit the bill. Tease Me, Please Me doesn't rely on chords so much but the main line is very repetative and will give you some good practice fingering individual notes.
Other easy songs to get you started:
- Ozzy Osborne Crazy Train
- Georgia Satellites Keep Your Hands To Yourself...
- Alot of early Metallica rhythm guitar is excellent power chord practice...Four Horsemen and their cover of Am I Evil.