Recently, I started gathering up items that I have been holding on to for no apparent reason, other than I hate to get rid of things, and selling them on ebay. I'm sure you've thought of this, but might think it's not worth the effort. When I first tried it, it was a little daunting at first, but after the first or second posting, it becomes extremely easy, as the process is the same for each item you sell. I sold 5 items, and made over $500. My goal was to sell/save enough to buy a new, more expensive camera that I would never have just gone out and dropped $500 on, but having sold items until I got that amount of money, I didn't feel so bad getting the camera! I keep looking through my house for things I can part with that are basically just collecting dust, as I am now selling to save for a jungle gym for my son. That's my next goal. I have sold things like designer purses, a camera I got a year or so ago and never liked, my son's barely used nursery ensemble, his collection of Sesame Street plush toys used as decoration in his toddler room, his Leapster/games/backpack that he picked up once and never looked at again, that kind of stuff. When you get in the mindset of getting rid of the things you don't use or can part with, you'd be surprised what you can think of to sell.
Good luck to you! I'm a single mom too, so I know it isn't easy to make ends meet, but you sound like you're doing a terrific job!!!