One of the more interesting and simple to use Web search tools I've come across lately is Boolify, an educational tool that teaches you how to use Boolean search operators in a visual way. Here's how it works: you start with a green puzzle piece, type in what you're looking for (I used "how to knit"), figure out what you don't or do want in the results by adding the "and" or "not" puzzle pieces, and you're off and running.

More on Boolean search

Boolean searching is built on a method of symbolic logic developed by George Boole, a 19th century English mathematician. Most online databases and search engines support Boolean searches. Boolean search techniques can be used to carry out effective searches, cutting out many unrelated documents. Learn more about Boolean search.