With Google trends you can compare words, and see how they are being used within google searches. You can use it to compare different things.

Check it out at http://www.google.com/trends

For example, I did a search on MySQL,PostgreSQL,Ingres to compare open source databases.

To see how google stacks up with the commercial competitors I tried. MySQL,Oracle,SQL Server,Informix,Sybase

Check it out, it’s very cool