I posted on blogroots about an RSS-to-IMAP feature over at Blogstreet, but I have to mention it again here because it's one of my favorite new things I've seen in the world of weblogging. I share time between operating systems, so none of the myriad of RSS readers worked for me in the long run. Reading weblogs via IMAP email across two computers works beautifully, and you can even forward posts onto your blog through email. I've also noticed I can keep all the messages and essentially have a searchable, personalized archive of weblogs I read. If I remember hearing about a crazy new doohickey that was mentioned somewhere a few weeks ago, I can find it with a keyword or two in my email app.
Aside from weblog software, this is one of the first features I'd pay for, if I could.