Browsing the Web Using Google Cache
Google Cache is a great solution if a web page is down. If you're visiting a site and it returns a "404 error message", you can try to do a search on Google for that site adding the cache: operator, e.g. cache:www.google.com.
Check Spelling Frequency with Google
This is a quick and easy way to check the relative frequency of spellings. Query for a particular spelling, making note of the number of results. Then click on Google's suggested spelling and note the number of results. It's surprising how close the counts are sometimes, indicating an oft-misspelled word or phrase.
Translate a Single Word
Translate a single word Google Translate has added a nifty new twist: dictionary translations. For instance, say you're looking for ways to say "drive" en Francais; you can plug it into Google Translate and figure out that there are different ways to use drive, depending on the context.
Phone Number Geolocator (USA & Canada only)
Google Maps mashup Phone Number Geolocator takes the first six digits of a phone number (the area code plus 3) and gives you a close approximation of that number's origin on a Google map. Google has been helping us locate area codes for a while now, but some area codes cover pretty large areas. The NPA-NXX Geolocator goes one step further and narrows the location down to a more specific and accurate estimation.