For an intermediate level, I found that a lot of Dave Matthews Band songs make for great practice and are a ton of fun to play. There are countless riffs and chord progressions that are extremely satisfying. Also, it's a good chance to work on upbeat and aggressive strumming patterns.
Here's a few of my favorites (all great songs) :
Tripping Billies (good for practicing rhythm & strumming)
The Stone (good for flat / finger picking)
Dancing Nancies (good one to start)
#41 (the easiest in the bunch imo)
Try checking them out at : http://www.dmbtabs.com
Otherwise, here are some other suggestions:
My Friends (Red Hot Chili Peppers)
Hotel California (Eagles)
Jolene (Ray LaMontagne)
Layla (Eric Clapton)
J.