Here is a directory of some DVD & Blu-Ray Disc Suppliers. I have used some of these to source products to resell on eBay, and others I have never used. Some have a great selection and others only have a few.

Ingram
Baker & Taylor
VPD
A&E Bulk Lots
Brandywine Liquidators
Time/Life
Graveyard Mall
Glory Days Entertainment
Frontier Video
Wax Works
Buy-Rite DVD
DV&A
First Video Exchange
Super Discount CDs & DVDs
Wholesale Discs
World Wide Liquidators