Method 1. Directly Export iMovie project to AVI using iMovie '08/'09/'11/HD
Actually, exporting iMovie project to an AVI file could be as easy as ABC with iMovie share dialog (for iMovie '08/'09/'11, go to Share > Export using QuickTime; while for iMovie HD, go to File > Export > Quicktime > select "Expert Settings" from the popup option > click Share). From this iMovie share dialog, you are able to choose the file format you want to export to from the Export pop-up menu (Choose "Movie to AVI" rather than the default option "Movie to QuickTime Movie"). Click "Save" and you will get an .avi file from iMovie.

Note: You can customize your movie settings by click on the "Options" button.
Method 2. Convert iMovie to AVI (Rawvideo/DivX/XviD) using iMovie to AVI Converter
If the first method is not working on your Mac, or the exported avi files have playback problem, or you want to export iMovie to other video format with high quality, this iMovie to AVI Converter Mac could be a better choice for you to convert iMovie to AVI format, as well as any other popular video formats like MP4, M2TS (AVCHD, H.264), FLV, MOV etc. With this Mac Video Converter (Mac OS X Lion included), you will never worry about video format problem when importing AVI to iMovie or exporting iMovie to AVI videos.
More iMovie tips: burn imovie to dvd, import m4v into imovie, convert mpg to imovie, import mp4 into imovie

