The Cloud Storage – Dropbox is the most popular page here. Since I posted it, I have gathered a few more links relevant to the topic. I have updated the original post to include them, but here is a quick post to highlight that change.

http://dereknewton.com/2011/04/forensic-artifacts-dropbox/
http://forensicartifacts.com/2011/07/dropbox-config-files-windows/
http://computer-forensics.sans.org/blog/2011/06/17/digital-forensics-rain-drop-keeps-falling-on-my-box
http://www.forensicfocus.com/dropbox-forensics