Well, here are a few of the MU*s I'm on, and some information about them. I'm only including ones I'm currently on, not ones that I've left. :)

Mercyground is currently the one I'm planning on spending a decent amount of time and effort on. It's run by quite a few friends of mine, who are some of the best Admin I've ever met and worked with. It's a World of Darkness MUX set in Washington D.C. in modern day, with open Character Generation combined with an application process for some of the rarer/more powerful Supers (certain Bete and Clans, mostly). It can be found at mercyground.org 9999.

I play Jaeger there.

FurryMUCK is someplace I'd always heard rumors about, and never actually visited, until one day when I was really depressed and my blood pressure was skyrocketing, and I really needed someplace to relax. I dropped in, created a character named ThrowsCars, and went off and made lots of friends and had my blood pressure drop by 20 points on either side within 2 weeks. It was quite fun, and I took the opportunity to build a massive forest, which also calmed me considerably. Something to keep the creative juices flowing, finally. :) It's at furry.org 8888. It's a must for anyone who's ever wondered about it after hearing rumors. :)