Desktop Nexus - Huge collection of wallpapers. The site also detects your resolution and changes the size for you to preview before you download.
10 minute mail - When you don't want to give out your email address use a temporary one. With a handy option to extend the time if you need to.
Martin Lewis' Money Saving Expert - Lots of offers and deals. Personally I regularly visit here to get free tickets to films, often before they come out.
Google Real Estate Search - Find property for sale or rent in a specific area. Narrow it down with by price, bedrooms and bathrooms and check Google Maps for the red dots. Click them and see a thumbnail of the property and price, click that to get more details from the site it is listed on. Useful for the satalite view to see what is around the property you are interested in.
Atari arcade games - Not exactly useful, unless you want to a fun timewaster. Play the old arcade games in your browser.
Down For Everyone Or Just Me? - Check if a website is down. Helpful at work to stop getting the blame when it is not your fault. We are always getting blamed for blocking websites.
Draw Anywhere - A free online replacement for Mircrosoft Visio.
Carryout Text - Convert just about any text file into an MP3 for listening to at work, in the car, on your MP3 player etc. Free while still in beta. Currenly English text only.