From an old-time usenet user:
You need to find a good feed (which should be free if you've got a good ISP/DSL provider) and you need a good newsreader, of which there are many candidates (I get by with gnus for the moment; I like nn when I can get it. The google groups interface started weak and has gotten worse with the new "beta", I don't use it for anything but searches). You microsofties: consider the fact that you can run a text-based newsreader in a ssh session.
From a technical point of view, usenet has a number of advantages over the web: it's far more decentralized: it can't be slashdotted, it doesn't get nailed by a single server outage . Because it's text based, there's none of the point-click-and-wait folderol you tend to get stuck with in using a web interface (I'm typing into a mozilla textarea now, but a newsreader would have kicked me into my favorite emacs).
As far as social dynamics goes, well the bad news is that the web is where the action is, and the good news is that the web is where the action is. The eternal September has definitely ended. Usenet is a place you can go for the wisdom of the elders without being too annoyed by silly kid stuff. The perl groups are okay by me, and I stop by there on occasion to see what's going on (though I don't mess with *.moderated much, the moderation system has never let me post to it, for whatever reason).
A hint for using usenet though: the social standards are collegiate rather than corporate, so if you're the kind of twit that gets bent out of shape by someone calling you a twit, you might as well stay off. Grow some skin, and learn to ignore insults, or stick to a moderated forum.
Oh, and there are definitely some non-technical newsgroups that are worth a look.
 It was funny watching the livejournal crowd slinking back to usenet for their net-fix back during the recent LJ outage.