Wikipedia is often vilified for its accuracy (rather, the lack thereof), but it is still a very useful starting point for research. Uber-geek and PhD candidate Kevin Lim, who researches online communities, talks to high school students about how to use Wikipedia in the classroom.
He gives terrific advice, talking about Wikipedia clearly and accessibly. While the talk was tailored for the equivalent of Junior College students here, it's useful for undergraduates too.
You can view the video* at the top and follow with the slides (above).
Read Kevin's post at theory.isthereason.com.
* A pity it gets cut off during an interesting question at the end.