GCFA - GIAC Certified Forensic Analyst
I mention this first simply because I took the training (SANS SEC 508) that it tests you on. It is generally not considered to be THE forensics training to get, but I don't think it's totally ignored either. The cost is listed at $800 (as of today), but it's $300 if you sign up for it along with the SANS SEC 508 class.
I paid for the certification attempt when I went to training in November, but haven't studied yet, let alone taken the test. I'll update this when I know more.