I may be old-fashioned or out of fashion but I've been reading news groups with Thunderbird (and SeaMonkey and Netscape before that) -- the alt.os.linux.slackware group plus the Mozilla groups, but I have to admit that I only look at any of 'em about once a month nowadays...

Claws does newsgroups also.

When I still read usenet, I used lynx. It's not a very powerful interface, but it's fast, exposes header information in a useful way, and offers good ergonomics.

About six months ago, only two of the newsgroups I followed were still at all remotely useful, and neither of them were exactly great anymore. So I found some web BBS's to replace them (and linuxquestions.org was one of those). I'm unlikely to renew my newsguy account.

"tin"-user since the late 1990s - it's fast, easy to use and distraction-free. However, "newsgroups" usually means "news.gmane.org" these days. For actual newsgroup access I'd propably use "nzbget", theoretically speaking, of course.