We're Mac so the choices are pretty simple and painfully few: Adobe Premier Pro CS5 or Final Cut Pro. Both are fully-featured editing programs which will allow you to do everything you have ever wanted with your video. Which means they take a lot of time to learn how to use effectively. Final Cut Pro is the closest to the Avid programs Linda used to use in her studio work so that's what we are currently using but it's a bear to learn (said the guy who is trying to learn it :))

If you are PC-based, the choices are more numerous and you have some good budget-friendly pieces of software. Be sure you can import your files from the 5D directly without converting them.

Jim