You can't export a completed slideshow (w/music and transitions) from iPhoto to iMovie using iLife "08". You can export the slideshow to iMovie HD,,, which is the previous version and then send it to iDVD. My objective was to make two slideshows with music and transitions,,, then have them play consecutively. Sooooo,, if you make your slideshows in iPhoto,,, you can export them to the prior version of iMovie which is iMovie HD,,,,edit them how you wish,,,, then send them to iDVD for burning. According to the "Missing Manual" by David Pogue,,, it's a good idea to have both on your computer anyway as you can switch your project from one to the other and use the best of both worlds. iMovie 08 doesn't have many of the features that iMovie HD.
Regards,
Bill