I'll start off the Windows 7 cake-ness with taskbar tricks I've culled from various places that I've been using this evening (some of which I've seen for the first time in the past few days, despite that I've been using Win7 regularly since the RC):
Win 1-9 start the corresponding pinned application (from left to right; wonder if this switches to right-to-left in RTL locales?)
Middle click on a taskbar icon opens a new instance, as does Shift+Click (or Win+Shift+Number).
Middle-click on a thumbnail preview closes the window.
Ctrl+Shift+click opens a new elevated instance of an application.
Ctrl+Shift+Win+Number (for those with extra fingers) also opens an elevated instance of an application.
Right-click on a thumbnail preview opens the window's system menu (like right-click on an old taskbar button did)
Shift+Right-click does different things depending on how many windows the application has open:
One window: Opens the window's system menu.
Multiple windows: Opens a context menu with options to cascade, tile, and close all windows belonging to the application.
I <3 the new taskbar 
Only taskbar "power-user" feature I'm missing is that you can no longer Ctrl+click to select multiple windows and close them... makes it difficult to close multiple windows from different applications, but I'm not sure how you would implement this given that individual windows aren't always visible in the new taskbar. Yes, I have used this one before, and I actually wished I had it earlier today... doesn't come up very often, though.
WindowsClient: You know your post rate has gone down...
Silverlight: Geek Profiles – Scott Guthrie
