What hotkeys do you use to make your life quicker and easier? I'm using Windows 7, I know the windows key + space is something different on other versions of windows.

-Windows Hotkeys-

Windows Key + <Number 1-0>: Opens the corresponding window on your task bar.
Alt + Tab: Switches applications, starting with your most recent ones.
Alt + Shift + Tab: Same thing as above, but backwards!
Windows Key + D: Minimized all your windows to show the desktop, hit it again and it brings the same windows up as before.
Windows Key + Space: You have to hold the windows key, and it just makes all the windows invisible.
f2: If you have a file selected and hit f2, it will let you rename the file.
Ctrl + Shift + N: Makes a folder.

-Browser Hotkeys-

Ctrl + Shift + T: Restores closed tabs, starting with the most recent.
Ctrl + T: Opens a new tab.
Ctrl + W: Closes current tab.
Ctrl + Tab: Switches to your next tab.
Ctrl + Shift+Tab: Switches to your previous tab.
f5: Refreshes the page.
f6: Select the url.
Ctrl + +: Zooms in the browser. (You can use the scroll wheel, for this and the next one.)
Ctrl + -: Zooms out the browser.
Ctrl + 0: Sets zoom to 100%.

-Text Editing Hotkeys-

Ctrl + A: Select all.
Ctrl + C: Copies what you have highlighted.
Ctrl + X: Cuts what you have highlighted.
Ctrl + V: Pastes whatever if in your clipboard.

Shift + <Left, right, up, or down arrows>: It highlights a letter at a time.
Ctrl + <Left, right, up, or down arrows>: Skips your cursor over words at a time.
Shift + Ctrl + <Left, right, up, or down arrows>: You guessed it, lets you highlight words at a time. (The two above combined)

That's all the ones I use that I can think of, tell me which ones you use, or if there's any you use that I don't! I also urge you to start using some, makes you much more efficient.

EDITS:

Windows Key + P: Give you display options for duel monitors and such,
Windows Key + R: Brings up the run windows, I typically just use it to launch notepad. So you'd type 'notepad' in.
Windows Key + X: I use this one on my laptop all the time, easily can change my brightness, volume, and battery performance.
Ctrl + F: You can type for words you want to find on a page. You can also highlight a word, then ctrl + F to auto type that word in.
Ctrl + H: In a text editing program, you can specify a word, and what to replace that word with, be careful...