This article suggests using 'wordle' to create a 'word cloud' from a selected text. It works really well in historical sources (or modern articles) for bringing out key terms. It's also a really efficient way for students to 'scan' a text to see if it might be relevant when researching - particularly for those who read slowly, or for ESL students who are daunted by large blocks of text - and it looks very nice too!
This seems to update with interesting topics that students might find relevant for research or for classroom activities. I use Bloglines to subscribe to the feeds on sites like this (Google Reader is also good) and that way I only have to go to one site to keep up to date.