For anyone who enjoys good music, good times, and good people, music festivals are always a great place to experience all three with a good group of friends. Both festivals are four-days long and its recommended you either camp or stay in an RV for the full experience.
Bonnaroo
It has been going on for a few years now and it is starting to be more of a "mainstream" festival with past headliners including Jack Johnson, Metallica and Pearl Jam. I went two years ago when the headliners included Radiohead and Tom Petty & the Heartbreakers (with a surprise guest Stevie Nicks). Here are a few pictures from my experience:
This is the Entrance to "Center-Roo" where all the concerts are held.
This is the Mushroom Fountain, which is now a lot more colorful than this picture.

Main Stage During Moe.

This was our campsite which was very crowded but we were surrounded by great people.

Rothbury
Rothbury in my opinion was a greater experience for the fact that it is less main stream but still big names. The first ever Rothbury was held in 2008 and was an amazing experience, with headliners including Dave Matthews Band, Widespread Panic, John Mayer and 311. Here are a few pictures from my experience.
Main Stage:

There was a lot of great artwork:

Both festivals take place in the summer season with tickets around $250, but early birds can get cheaper deals. Plus, its worth the money hands down. For more information on the festivals visit their websites: