Microsoft released the Visual Studio Team System Web Access 2008 Power Tool.
Team System Web Access SP1 lets you do all the things you can do in Visual Studio in your browser. You can view, create, and edit work items, associate work items with each other and with changesetsand view source, diffs, changeset contents, and branches.
SP1 also includes what was once called TFS Work Item Web Access. Work Item Web Access lets users without TFS licenses submit and view work items through the browser.
With a little SharePoint magic you should be able to frame Team System Web Access within your existing team sites.