Running with the bulls was one of the most thrilling and scariest experience I have ever done. Here is a video of the second day I ran in Pamplona during the San Fermin festival.
If you are interested in running you just have to show up an hour to an hour and a half before 8 am. There are no waivers to sign you just have to get by security who are just looking for impaired runners.
The festival last from July 6th to July 14th and there is a run every morning starting on July 7th.