Oh Yes, these definitely exist. I belong to a couple in fact. Most of the sexual Muds are furry meaning that you create a character that is an athropomorphic animal and play them. There's everything from vanilla sex to BDSM on these mucks, but the great thing is that you can choose what species you prefer to play with and such. Some people think furry is sickening because some of the people in the fandom do sick things. That doesn't make everyone bad of course. If your interested in trying out one of these sign up for a character at www.fur.com/tapestries after you register your name then simply download a program like smud or gmud or mushclient or something to run it on.
There are some very sexy people on the role play areas. It's a ton of fun and great for when you are waiting for a post from someone on here. I will tell that 99% of the characters you find on mucks walk around in human clothes and live in human houses. If you can get around the animal part your all set to go.
If you have any questions just let me know.
Here is a an example of some furry art just so you can kinda see the concept http://vcl.ctrl-c.liu.se/vcl/Artists/Michael-Higgs/tristan-undies-color.JPG
*giggles* Who don't I play?
Too many to list unless you want the long drawn out one.
The ones I play the most are Snowshower, Aneska, Nashoa, Raindancer, Cheyenne, Rainy and Dusty
Who are you on there?