I found a website that has loads of yo momma jokes on it. well its on a page at wikipedia.co.uk. If you type in Your Mother in the search box it comes up with a page packed with yo momma jokes. Here is the exact link: http://en.wikipedia.org/wiki/The_dozens Also there are some links at the bottom of the page. Here are some of the good ones.
Yo' Momma's so ugly she makes you look good(a double diss)
Yo' Momma's so fat she went to an All You Can Eat buffet and they went broke.
Yo Mommas so fat .she went on the scales and it came up with your phone number.
Yo Mommas so old her breast milk is powdered.
Yo Mommas such a slut she has more Wangs in her than a Chinese phone book.
Yo Mommas so ugly when she was born her incubator had tinted windows.
Yo Mommas just like a television. A 2 year old can turn her on