Just here on Literotica? Oh yeah, I've got a few favorites:
* A Birthday to Remember by incest0
A middle aged bellydancing mother "entertains" her son on his 20th birthday. Short but sweet.
* Getting the Very Best of Mom by Anal_King
A son blackmails his big assed 48 year old Colombian mother into anal sex.
* Tabootopia - A Nation of Incest Ch. 04 by Surt
The whole series is great. Hot female celebs like Shohreh Aghdashloo and Necar Zadegan have sex with their sons. And everyone else.
* Mom's Milkshake Mustache by Adom&Eav
Just great. Lots of incest, lots of hot sex in general. Loved it.
There was also an excellent story about a son who finds out that his mother is a witch, and she transforms them into snakes and they make love on Halloween, but sadly it seems to have disappeared.