Changedection.com is a site that lets you monitor a webpage to see if it has changed. If it does change you get an email. Ideal for tracking a site that doesn't have a RSS feed. I got tipped off about this site a few week ago at the IRE confernce. I tried it out and have been impressed.
After signing up for an account, I entered a the url for the site I wanted to track. I then got brought to a page that gave me a lot of options; Do i want to be notified only if information is removed from the page? Or if it is added? How often to receive notification? Most importantly they let you enter a word that must appear on the page before you are notified.
When the page changes you get an email that contains a link to the changedetection site, where they show a summary of the new information (highlighted) and the removed inforamtion (crossed out).
I haven't had a great need for this tool yet, So far the most useful way i have put it to use is on the websites for annual conference. Now if they add the word '2010' I will find out and get a head up on the when they update their website with information on next years conference. However I am certain this tool will come in real handy in my research at some point.