Here are three domain registration programs from Shareasale:
a. EPC: $9.50 - Tracking Gap: 120 days - Commission: $66 per sale
b. EPC: $25.97 - Tracking Gap: 60 days - Commisison: 600% per sale
c. EPC: $7.18 - Tracking Gap: 90 days - Commission: 35% per sale
There are TONS of domain registration programs out there, and the most popular seems to be HostGator.
You need to check out the creative and the offer and see what would appeal best to your visitors. This is from my post The Best Affiliate Program.