Anyway, while I was playing around at the hackfest they introduced heroku, which is a cloud platform for ruby. Heroku uses git to let you manage your application's files on the server. Pushing a brand new repo creates a new domain name and sets up the infrastructure for your app. They built a very cool application on top of the git platform.
Github has been doing this for a while. I blogged earlier about github and the things they've done with git. The most public things include git as a blogging/wiki engine as well as a static website generator (github pages). You can also fork git-achievements and broadcast your mastery over git, like I did. Honestly, the things you can do with git are endless since it is, after all, nothing more than a versioning filesystem in user space.
I think this is the biggest thing that separates git from other version control systems. No one has done anything with SVN beyond simple pre or post-commit hook scripts. TFS has a lot of application infrastructure built around it, but it doesn't build on top of it's version control system. Neither does mecurial or bazaar, even though they are also distributed version control systems.
The git folks really focused on defining git as a standard rather than an application. By that I'm referring to how they defined objects, trees, packfiles, etc (see progit) instead of focusing on developing an application. For much of it's lifetime git was nothing but a hodgepodge of shell scripts and C libraries. Now days there are several varying implementations of git. The fact that git is so widely programatically accessible is making it insanely easy to leverage inside programs. I'm still waiting for a .NET app to do something big with git#...or maybe I could.