Want to access TFS Work Items via PowerShell? Then you'll want to check out the Team Foundation Server Project Browser PowerPack for PowerGUI

Dmitry’s PowerBlog: PowerShell and beyond - TFS inside PowerGUI

"Steve Crouse has recently published his PowerGUI pack for Microsoft Visual Studio Team Foundation Server - thus, fulfilling James Manning’s long time wish.

This is a very nice tool allowing for browsing the work items for all the projects on a Team Foundation Server either by area or iteration. In addition you can view all open work items assigned to you, regardless of project. Project metadata such as the work item editing form definitions can be viewed for each project.

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PowerGUI - [1852] Team Foundation Server Project Browser PowerPack

"Allows browsing of TFS projects by Area Path or Iteration.
Allows execution of stored queries for any project.
Allows viewing of work item attachments.
Multi-select a group of work items and click the 'Open vs. closed chart' action to generate a simple pie chart.

Must be run from a machine with Team Explorer installed.
Will prompt for the TFS server address.
Click the 'Change server connection' node to connect to a different server.

..."

TFS Work Items and PowerShell, two things that taste better together... (sorry, it's a Monday... ;)