Google Sets allows you to create sets of items from just a few items that you’ve entered.
Google Sets acts much like a online thesaurus in that it takes a word and gives you related words to this item. What makes them different is that they take more than one word and find the center of meaning and display items related to the overall theme of the phrases entered.
It’s a nifty little took for tagging items in blogs, or just giving you related keywords. Try it out at http://labs.google.com/sets?hl=en