The iMovie Plugin Pack 2.1 contains a set of effects, transitions, and titles that you can add to iMovie for Mac OS X. The iMovie Plugin Pack 2.1 includes the following new effects, transitions, and titles:
Flash, Ghost Trails, Mirror, Mirror Advanced, N-Square
Circle Closing, Circle Opening, Radial, Warp In, Warp Out, Wash In, Wash Out
Subtitle, Subtitle Multiple, Zoom, Zoom Multiple
More info and download links here.