Linus Torvald’s talk at Google, about Git, a distributed version control system. I screen-captured his slides, and they are available for download. I’ve been playing with git a bit in my personal projects. My workplace still uses Perforce though.
When on the road, I have the whole repo with me and can check-in my changes, revert, etc. When I get home, I can push my changes to my server and that can act as my “backup”. Although with Xcode 3.0 and its “snapshot” feature, I can sort of simulate this, but I would use that as a last resort though.