Apple has their main link for video tutorials set for the new iLife ’08. If you are still working with iLife ’06 (it does have some advantages over ’08), then go here for multimedia tutorials:
And just so you know, if you want to use both iMovie HD and iMovie ’08 (each has their own advantages), you can! They can both be installed on the same computer without issues. You can even run them at the same time.