FeedDemon is a highly-popular RSS aggregator that I have used for several years. Nick Bradbury developed FeedDemon, and he passes along the interesting story of how development of this elegant product came about:

I used to rely on email, but it’s almost useless to me now.
Funny thing is, if it weren’t for spam, I might not have created FeedDemon. As I’ve mentioned before, after spam and anti-spam filters made it impossible for me to communicate with customers by email, I dumped email and started using my blog and its RSS feed to communicate instead.
And that led to the creation of FeedDemon, which I’m having a blast working on. So I actually benefited from spam. Go figure.