Many say that Win-D minimises all applications. Not true. It simply shows the desktop. Use Win-M to minimise all open windows. Use Win-Shift-M to restore them to their previous state.
By the way, did you notice that the Sift key can be combined with most of the usual shortcuts? e.g. Alt+Tab : cycle through applications 1->2->3->4->...1 Add Shift to the shortcut and you will be cycling in the opposite direction 1<-2<-3<-4<- ...1
Control+Tab to switch between Tabs in most Windows applications (sadly not in Eclipse) - you can already guess what Ctr+Shift+Tab will do. Especially handy in Firefox, IE, etc... where you have more than one Tab open and try going to the previous one. Very handy.
And one more tip, this is soooo handy, I love it. Only found out about it a couple of weeks ago:
FireFox users: tired of rightclick->Open Link in New Tab
?
Click a link with MIDDLE mouse button and it will open in a new tab (depends on your Tabs settings in Tools->Options but by default would work). The magical thing about this is that it works even for the browser's Back button! Also when you type a search term into the Google box (usually in top right corner) and middle-click the search button, the search results are opened in a new tab. Closing tabs is also much easier with the middle mouse button (of course you can do Ctrl+W but sometimes the mouse is simply in your hand). You don't have to click the tab's red button to close it. Simply middle-click anywhere on the tab and it will be closed.
EDIT
I just tried the middle button in IE 7 and seems to work just like it does in FF, except for the Back-button and Search widget.