Must have links and resources you need to have to do a SBS 2008 migration:
www.sbsmigrationtips.com (aka the SBS blog post keys to success)
MPECS Inc. Blog: SBS 2003 to SBS 2008 Migration Guide – v1.0.1:
Active Directory Clean-up prep for SBS migration | Third Tier:
Windows Small Business Server 2008 Migration : John R. Pattison:
And if you are looking for a book on the process, David Overton has probably the best guide I’ve found because it explains the migration as well as gives screen shots. If you want to order a book you can, but the pdf feature is very nice.
Small Business Server 2008 – Installation, Migration, and Configuration: