Wixed
In one of my recent projects, I had to write an installer to deploy a web application. I tried the installer project built into Visual Studio, but it was not very flexible so I started looking around for another solution.
I remembered hearing some buzz a while ago that Microsoft had released an installer tool as an open source project. After a little searching, I came across Wix on Source Forge.
Wix stands for Windows Installer XML, which is pretty descriptive of what it is: a mapping of XML to the Windows Installer database. Although it is somewhat primitive, it has a very flexible command-line-n-text-file system that works well for simple installers. Definitely worth a look if you are building installers. Now if I can only get it better integrated with the rest of my Visual Studio project...