You can recognize sites that offer RSS by their RSS/XML buttons, like these:
You can also use Adobe Bridge as a RSS reader the way Matt Kloskowski is showing in his RSS Bridge Tutorial.
If you use Atom: Lunacore Photoshop Blog feed (Atom 1.0) : http://www.lunacore.com/blog/?feed=atom
The forum feed (RSS 0.92) shows the 10 most recent topics in the Lunacore forums. The Lunacore Forums feed however has to be added manually in your newsreader (copy/paste the link).
Note: some RSS readers will have an option that's called auto discovery, which will alert you when a web site is making use of this feature. Lunacore only makes use of auto discovery for the Lunacore Photoshop Blog. Autodiscovery allows you to automatically add the news channel to your favorite reader.