When you're too broke to go thrift-store shopping, you can still pick up items through Freecycle (as long as you have the money for gas, and the person posting the offer picks you as the recipient of whatever they are giving away).
Also, don't forget your local libraries as free sources of books, movies, and music. Check out "The Complete Tightwad Gazette" by Amy Dacyczyn.
Depending on your financial situation, you could get food through a food pantry (community or church), which would lessen your grocery spending.
Some good sites for other tips:
(good even for non-moms)
If you can figure out any good way to earn more money, and combine that with cutting down expenses that are less important so you have more money for the things you WANT to spend money on, that's the way to go.
It's kind of like losing weight: the best method is diet AND exercise. Money is like that too: combine earning more with spending less.
I don't know what your job skills are, but if you have products to sell, that can have potentially greater earning power than getting paid by the hour. (So I've heard--I haven't tried it yet.)
If you have an outgoing personality and you think you'd be a good salesperson, you might try selling Avon, Mary Kay, Pampered Chef, or something like that. I have a few relatives who sell Mary Kay and make some decent extra money to supplement the income from their primary jobs.