You can crop with QuickTime Pro! It's not efficient, but it's cheaper than buying iLife.
1. In an image editor, make a new image, completely white, with the dimensions of the frame size in the video, e.g. 640 x 480 pixels.
2. Make a smaller square or rectangle of the size of the crop (i.e. less than 640 x 480 in this case) and position it within the white image in the location you want the crop to be. Fill this inner rectangle with solid black. The black area will be retained, while the white area will be cropped away. For example, if you want to use the lower-left quadrant of the video, make an image like this:
3. Save the image as a PNG.
4. Open the video in QuickTime Player (Pro).
5. Hit Command-J to bring up the Properties window. Select the video track and go to the Visual Settings tab. Add your PNG to the Mask area of that window (you can drag and drop or click the Choose button). Leave the Transparency setting as "None (allow dithering)".
6. Close the Properties window.
7. Export (Command-E) the newly cropped movie to a format that iMovie will import (preferably something lossless).
8. Open in iMovie and continue your editing.
I bet it was. But does it involve cropping?