In the past, I've always used Github for my online repository needs. It has a wiki and issue tracking system for each repository as well as a very nice layout of the files in the repository, syntax highlighting and the ability to edit files from the website. In addition, it's got some very nice graphical representation of commits and contributions from individual users. The main drawback? Private repositories cost money.
However, I was recently recommended Bitbucket, a similar online repository website which allows free private repositories. I've decided to take a look at it, and so far I've been pretty impressed. It shares the features of a wiki and issue tracking system, which is a big plus as I like to keep my game design document online in the wiki along with the code. I haven't uploaded a repository yet, but I'm hopeful it will have similar features to Github. The fancy graphs may be missing, but how useful were they anyways?
I'll be using Bitbucket for one of my personal projects. We'll see how useful it is in practice, and I will report back with a full comparison of the two services for your viewing pleasure.