<p>I would like to access the work items in our TFS programmatically. Shouldn't there be an obvious command line tool to extract such information? Or a WebService I can just call? I already have checked into using Excel - this is neat, but I want more hardcore...</p>

Take a look at the TFS API (
http://msdn.microsoft.com/en-us/library/bb130146(VS.80).aspx
).  Access to the same code used by Microsoft to create the Visual Studio integration and their version control command line tool (
tf.exe
).
You can also take a look at the power tools.
tfpt.exe
is the power tool command line and has many other advanced features.  That said - you can do pretty much what you want with the SDK.
The new version of the power tools will be out soon, and that looks to have
Powershell support
coming
Enjoy!