Murphy Brown - Avery (thanks, Kristen!)
Roz Doyle - Alice
Agent Dana Scully - William (But was in one episode she had a daughter, Emily)
Angela Bower - Jonathan

AH! Thanks for the *reminder* Kristen!

Christine Sullivan - Charlie

Mary Jo Shivley (Designing Women) - Claudia and Quinton

That's all I can think of.

Alice on Alice

Kate & Ally were single working mothers.
Wilona Woods became a single working Mom after she adopted Penny on Good Times.

Although I mentioned her in the other thread "Single Working Females", she belongs here more.....

Elaine Nardo - Taxi (She has two of the most annoying kids in TV history because of how nice and corny they were, lol).

Cybill - Zoey & Rachel