If you are looking to extend Team Foundation Build using workflow activities, then the first thing you should do it take a look at the latest stable release of the Community TFS Build Extensions over on CodePlex. This is a collection of around 100 activities that can provide many commonly requested functions incluing running CodeMetrics and NUnit tests, creating a Zip archive, wrapping RoboCopy for deployment, updating AssemblyInfo files, running StyleCop, merging assemblies with ILMerge etc etc. Basically most of the building blocks for major common customization already done for you. Also – as it’s an open source project ran by the MVP community you have access to a bunch of great code that shows you how to create your own activity should you want to do something that has yet to be done (don’t forget to contribute it back if you can)
Great job to the team of folks contributingg to the community build extensions (many of which I am proud to call my friends) – I’m looking forward to seeing the project go from strength to strength now that they have their first stable release out the door.