Track Bloglines Readers
One of the downfalls of aggregators like Bloglines is that you never really know how many people are reading your site. With Bloglines in particular, you can see how many have subscribed to your feed but that doesn't necessarily tell you how often they actually read your stuff.
In going through the log files for my site, I discovered that there is actually a way to track this. In my RSS feed, I have the following piece of code sitting in the channel definition:
<image rdf:resource="http://www.shoppingpr.com/_images/j/banner.gif" />
Bloglines uses this information to display an image in the interface. It's a good way to add a little branding for your site where there normally wouldn't be any. But bloglines doesn't cache this like it does with your actual feed. Therefore, every time a user views your subscription, the image gets pulled from your site. Voila! Instant tracking!