If you're using MSBuild to handle your builds and continuous integration cycle, then you should definitely take a look at the Enterprise Solutions Build Framework on Gotdotnet.

This is a vast collection of tasks to handle all manner of build-type tasks. It's been produced by Microsoft Services in the UK and represents their best practice for handling complex integrations.

There is a huge list of tasks covering a lot of useful ground, and stuff that has been a bit tricky to do. Examples include automating Biztalk, automating virtual machines, detecting network presence, security and certificates, FTP, XML, file and folder tasks, installer tasks (Wix, MSI, Cab), ACT, tools (NUnit, NDoc, FxCop, PSExec etc.) and a load of 'utility' tasks such as GUID creation.

Anyway, that doesn't really do it justice. You need to take a look at the helpfile for a better overview of the contents. If you're serious about build and integration, you need this library!