OpenWrap is the premier package manager for .NET.
Any .NET project beyond "hello world" is going to require external libraries and tools. There's an abundance of free, open source libraries out there, but how do you get what you need? Manually searching, downloading (and in some cases building from source) is not a productive use of your time. It's even worse when one library depends on another and you have to manage dependency chains!
The solution: OpenWrap
For example, say you want to use OpenRasta in your project. Simply run this at the command line:
o add-wrap openrasta-devtools
OpenWrap will query available repositories for the OpenRasta "wrap" and download it along with all the necessary dependencies, such as Castle.
Wraps are simple zip files containing the binaries, tools and other useful content. They are copied into your project in an xcopy-friendly manner.
Find out more
Sebastien Lambla, the creator of OpenWrap, writes about the project in his blog at CodeBetter.com.
There is a wiki at GitHub. You should probably follow seb on twitter as well!