There's a few guys on here (and elsewhere) that play a lot on crmod. I jump in from time to time. Had a pretty big game a few months ago. Sadly, there's not much else to speak of that I know of. When pcmagazine hosted some quakeworld servers for a week in celebration of quakes 20th bday, players came out of the woodwork. But other than that, I don't know what all the happenings on the QW side are.
As far as clients...if DM gameplay is your only concern, the latest MarkV is a good option. It has an updated network protocol (baker can give the details, he did the engine). Proquake (also baker) works well too. Spike has also done a new version of quakespasm (Quakespasm Spiked) that has a better protocol as well. These are netquake clients (this website primarily deals with netquake). If quakeworld is your thing, ezquake runs well on my machine, and my machine is pretty damn old.