all the usenet groups I ever use (a few music ones and tomb raider, all under alt.) are filled with crap. I looked in on the MC one this morning and that was full of rubbish. a shame really. I'll try other groups though.
I regularly look at, and contribute to uk.sci.weather. There are rather a lot of gadget nerds and people of the spotty-herbert tendency who seem to use weather as an excuse for computer exercises but there are also professional meteorologists who contribute, necessarily under a pseudonym. There is very little outright junk.