If you're looking for a free, professional-level video editor, Jahshaka for Windows and Mac should top 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; edit DV, SD, HD and film; do real-time 3D compositing and Flash animation; OpenGL-based paint; and it has a text module. There are also modules for color correction, keying, and tracking, and an array of media support. It comes with JahPlayer, a media player that claims to work with "virtually" all audio and video formats. Tested against all the major formats (MOV, AVI, MPEG, MP3, WAV, OGG) and some minor ones, too, we found it to be flawless.
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 for now you should be willing to wrestle with any problems that arise before you dive in.