I passed my GCFA about a year ago; and forensics and incident response have been my passion. However, as a DoD auditor, I don't get to the forensics and incident response jobs as much as I would like. Auditing is great, and I've been exposed to more and more of the offensive side of the security fence than I would have guessed. As a former application developer, I have gravitated towards the application pen-testing arena; and have learned much and really like it.
To that end, I feel my forensics skills getting a little rusty. So, I've been looking for ways to stay sharp. I started compiling a list of the various sites that housed test images. And in the process, I found that Forensic Focus has a good list:
Forensic Focus Test Images and Forensic Challenges
I'll update this post with other sites and compendiums that I find in the future.