Rotella releases a lot of total bullshit though, best to stick with his material as Anal Birth as it's the best. Ray Rivera is something of a bizarre genius with stuff like Black Putrefaction, but he is frustratingly hard to keep up with as he has a new project and label every few months. I like all his noise/gorenoise/electro projects a great deal.
Can't just leave it at those two either;
Marc Palmen - Urine Festival, Biocyst, later LDOH
Styv Pekari - Vomitoma, Black Mold Phallanx and 1000 others. Ran the notorious Splatterfuck and Mental Abuse labels.
Big Frog - Phyllomedusa, Macrophagous Gilled Larvae and more
I run a small label releasing things occasionally -
http://verminousrecordings.blogspot.com.au/