Here are some web resources for using & troubleshooting iMovie:

Apple's iMovie Support page

iMovie 08 Tutorials

iMovie HD Tutorials 

NCSU's Making Movies with iMovie 

 The "Unofficial" iMovie FAQ 

Macintosh Digital Hub - iMovie Resources 

Guide for iMovie 5  

Additional support is available from the Help Desk on the second floor of Meyer Library (by the Multimedia Area).