If you've got a sticker you need to remove, don't peel it off by hand. Use a hair dryer and it will just curl up and fall off.
This is a good one I reckon. If you've ever stripped a screw, try using a rubber band for grip.
I just saw a video that recommended sprinkling a cup of baking soda on your mattress, waiting a couple of hours and then vacuuming off. I might try it!
I just read a great tip to put those silica sachets from shoeboxes in with your tools to keep them from rusting.
Another good one:
Put electrical tape on a drill bit to avoid drilling all the way through a piece of timber.
Avoid getting unplugged when using extension leads by tying a loose knot. There's no strain on the plug ends using this technique. Great for when you need to go up and down ladders.
One for the gardeners: try spraying weeds with white vinegar instead of nasty chemicals.
This is a good idea when you don't have room to swing a hammer.