A tool called Google Sets featured on Google's Technology Playground - Google Labs is often overlooked and not many people know its great potentials.
Idea of Google Sets is quite simple and intuitive, it just automatically creates sets of items from a given few examples. For instance, you provide Google Sets few examples of colors like "Red", "Green" and "Blue", it will come up with more examples of colors which could later form a larger set.
If above example does not appeal to you then think again. I will give a more realistic scenario, say you are trying to find some alternatives for file archivers like winzip or pkzip. Try it with Google Sets and you will be amazed when it is suggesting additional terms for your set by considering words that might appear together in lists on Web pages etc. you may find the results you receive more useful.
You may see some irrelevant results but the idea here is not level of accuracy but the exposure to a set of suggestions that could give you some idea.
All said and Done:
Google Sets is really an amazing tool and can help you find suggestions for forming your set.
For further reading, please take a look at How Google Sets Works by Bill Slwaski
Technorati Tags: Google Sets, Google Labs, Tool, Google, archivers