RSS.NET - new build
RSS.NET is an open source class library which reads and writes RSS reeds. The project is still technically in beta and has never officially released a build, but a lot of applications are using it. I've been using it for a while and am very happy with it, but it has been a little disappointing to see this project linger in beta limbo for a few years now.
I was happy to see some recent CVS checkins with improved date handling a few weeks ago, not just because date handling in RSS is problematic, but because it's great to see some activity on this extremely useful library.
You can grab the latest RSS.NET build here (tar format).[1]
And here's a great article on using RSS.NET and it's evil twin, Atom.NET.
[1] If your zip program doesn't like tar's, I recommend IZArc.