A few others of my own...
1) Try using a few of the Windows Key (WK) shortcuts.
WK-D is really useful as it minimised every window, showing you the desktop without you having to go through every window and click the "minimise" button. Also, WK-E launches the Windows explorer. Not really customisations, but they definitely save time.
2) Use the taskbar toolbars.
Right-click an empty area of the taskbar, and you'll see a menu with an option called Toolbars.
The Desktop and Quicklaunch ones are the most useful. Desktop gives you access to any item on your desktop without having to minimise every open window, and you can use Quicklaunch as an alternative Start menu, only quicker and cleaner.
You can make the menus take up only a little space in the taskbar by unlocking the taskbar and dragging the menus over to the right-hand-side of the taskbar. Lock the taskbar again to get rid of the drag handles and gain space.
You can customise the Quickstart menu by dragging and dropping shortcuts from the Start menu (or your desktop) onto the menu itself (hold the control key to copy them).
You can also add your own toolbar by using the "New Toolbar..." option and pointing to any folder. Put shortcuts, documents, subfolders, whatever in this folder and you can have your own optimised toolbar.
3) Not something for everyone, but if you can, consider getting a 2nd monitor.
Most new PCs these days have dual output, so use it!
Having 2 monitors might seem like a totally unnecessary luxury, but it does save time if you do any design or programming work.
You can have a design/code editor window open on one, and a preview/runtime window open on another.
It's useful even if you just work with lots of powerpoint presentations or word documents. You can set Powerpoint to run the presentation on one monitor, leaving you to edit the presentation without interruption on the other.
