shelltwit allows you to update your twitter status via command line.
It's a good example of twitter API calls with xAuth. It also has bit.ly integration for url shortening.

Little more (?) info about it at the original blog post

You wiil need to remove the references to my sebagomez.snk files in three projects. After removing those you will be able to build the solution. (Now in Visual Studio 2015, requiring framework 4.6)