I also use the dejanews/google search engine to search for info on a specific topic. I'm amazed at how much there is out there. You can limit your search to reduce the amount of "noise" from non-relevant groups in your search result.
I love the Photoshop newsgroup that Doug posted, but don't have the time to monitor it every day. It quickly becomes overwhelming for me, though often tons of good information. Luckily, Doug monitors it or I might have never found this forum!
I also follow the scanning newsgroups every so often - again when I have time. I always learn things, but can easily get "lost" in all of the information, so find that using the search engines is a better use of my time when I have something specific I'm looking for. Often, my question has already been answered a half a dozen times already, so not only do I not have to ask a question that's already been asked, I also don't have to wait for the answer since I've already found a bunch!
Jeanie