If you're looking for a free program with the video and audio editing capabilities of professional-level software, Jahshaka should be tops on your list. With every release, it gets more stable and gains more features.
The list of what the application can do is extensive and exhaustive. It can handle real-time image processing with node based effects; editing in DV, SD, HD and film; real-time 3D compositing and Flash animation (up to 32k matte layers); OpenGL-based paint; and a text module. There's also modules for color correction, keying, and tracking, and an array of media support. The app also comes with JahPlayer, a media player that claims to work with "virtually" all audio and video formats; we tested it against all the majors (MOV, AVI, MPEG, MP3, WAV, OGG) and some minor ones, too, and found it to be flawless. The JahPlayer is supposed to work on Nokia cell phones, although we didn't have one handy to test that on.
Promoted as cross-platform, able to function with Macs and Linux as well as it does with Windows, Jahshaka has the potential to drastically change the am-pro animation scene. However, as an open-source application, it's not going to run perfectly yet, and so we recommend it at least for intermediate users willing to wrestle with any problems that arise.