Visual Studio 2005 Documentation
If you have installed Visual Studio 2005, and have not checked out the documentation included with it, then you need to. Go to:
Start->All Programs->Microsoft Visual Studio 2005->Microsoft Visual Studio 2005 Documentation
This new documentation app has a couple of cool features, and a couple of bugs that still need to be worked out. By far, the coolest feature is the Search. When you do a search for a topic, it searchs your local copy of the documentation. But it also searches MSDN Online, the Codezone community, and the MSDN Forums. Here is a screenshot:

When you select a section, such as the MSDN Forums (referred to as Questions in the Documentation, for some reason), it actually returns a snippet of each post, enabling you to quickly determine if the post is relevant, and if you want to click-thru to the forums. This is also true for MSDN Online and the Codezone community. I have found this to be extremely useful.
There is one thing I don't like about the documentation. When I use the online help (http://msdn2.microsoft.com), when I click on links on the right-hand side of the browser, to navigate to different topics, then the contents on the left-hand side adjust appropriately, to show me where I am in the tree. However, with my local copy of the documentation, that does not happen. Here is an example: I do a search, in my local copy of the documentation, for "team foundation". One of the returned hits is a link to the Team Foundation Overview. I click that link to open the Team Foundation Overview page in the right-hand side of the documentation window. In the left-hand side of the documentation window is the table of contents, represented in your standard tree-view. I would expect, once I had selected the Team Foundation Overview link, for the table of contents view to expand automatically to the node where this information is kept. That way, I know where it is in the contents. But currently it does not do that.
Like I said at the beginning, I think the search feature is cool and definitely worth using. Check it out for yourself and let me know what you think!