If you're interested in writing as a career, it might help to become a subject matter expert in a particular field. It's not always exciting, but it's a great way to carve out a career working from home.
I am a technology writer and it's pretty lucrative in terms of freelancing. Granted, I spent several years working in the field, but if you worked in a particular area prior to becoming a SAHM (finance, technology, etc.), you might consider writing for trade publications or for a company doing case studies, newsletters, website writing, etc.
It's tough now because my three kids are all under 6, but I am able to make a good living writing part time, and should be able to make a terrific salary when they're all in school.
I have friends who have been successful in freelancing for larger regional papers but they do it for love and not money. Newspapers don't seem to pay that well but in general, companies and trade magazines do.
You should also check out the 2009 Writer's Market book (just search for Writer's Market on Amazon) or check out their website at
Writer's Market - Where & How To Sell What You Write. The Writer's Market lists different publications that publish material written by freelancers and gives contact info and marketing advice as well.
Best of luck!