Hi R.,
I hope I don't duplicate advice; I read through the responses quickly for my own benefit!
Breastfeed your new baby. See if you are eligible for WIC, especially if you do not return to work. Ditto for food stamps.
Get "The Tightwad Gazette" books by Amy Dacyzyn (hope I spelled that right) from your library and read them for more ideas.
Instead of using paper napkins and towels, use cloth napkins and cleaning rags. Even though you wash them it is still cheaper according to Amy D., above.
I have not done this but have heard that Wal mart will match the sale price of any other store's ad. So you could shop there but get the equivalent of all the other stores' specials, as long as Wal Mart has the same item. Just bring in the rival store's ad and show it to the cashier when you check out.
Get a head start on making home made soups by saving any cooking liquid that is left over from meats, veggies, etc. and freezing it until you get a bunch (for me, usually a quart or so). Also if there are only a couple spoonfuls of veggies left, throw them in too; also rice or noodles. I have three freezer containers, one each marked "Chicken", "Beef" and "Veg." When one of them reaches "critical mass" I thaw it and make soup! I usually add carrots, celery, onion, especially if there weren't any of those in the freezer container. You can add rice or pasta as well. Don't season until you have everything in, because it will have all the salt etc. from whatever you froze, and it is easy to over-salt.
When your bottles of catsup, steak sauce, salad dressing are getting almost empty, turn them upside down when you put them away, make sure to TIGHTEN the cap! When dressing bottles are just about empty, pour a little vinegar or lemon juice in the bottle, slosh it around to get the last little bit out, and use that as dressing.
I make my own salad dressing and save a bundle--just combine lemon juice or vinegar, oil, mustard, garlic, and whatever herbs you feel like. Shake and refrigerate.
When spaghetti sauce jars are empty, pour a little water in, slosh it around, and freeze in your "Veg." or "Beef" containers.
We use lots of Aveeno and Cetaphil hand lotions--not cheap so I hate to waste them. If lotion is in a plastic tube, store it with the cap end down. When you can't squeeze any more out, cut the opposite end, reach your finger in the tube and grab the amount you need. When you can't reach any more, cut the tube again, closer to the cap. Keep going until there is no more tube. If lotion thickens or hardens, add a little water.
We had lotion in a pump container that had a bunch left inside but it was all sticking to the sides, so it wouldn't pump. I had a small plastic jar (used to have bouillon cubes in it) so I turned the lotion bottle upside down and let it drip into the jar. The jar has a good sized opening so it is easy to reach in for the lotion.
If you don't mind putting on deodorant with your fingers, you can easily extend the life of a solid deodorant container by a couple weeks. When you get down to the end of the deodorant you will usually see a sort of "grid"-like thing, that holds the bottom of the deodorant "column"--you'll sometimes feel this as you apply the deodorant to your underarm when you are running low. Just dig the deodorant out of the "grids", and smear it onto your armpit. Another alternative which I haven't tried but intend to soon, is to dig out all the deodorant from the grids and smoosh it onto my new deodorant--this saves having to wash hands after applying it with fingers.
Pack lunches and coffee break snacks for your husband (and yourself if you go back to work).
Roast a whole chicken for several meals, then pull all the meat off for sandwiches, casseroles, etc. Put the carcass into a pot with water to cover and make chicken stock for soup. Same thing can be done with beef bones.
Don't waste leftovers. Almost anything can be made into a casserole or stir-fry or soup. Yes, sometimes it may not be the most delicious thing you ever ate, but on the other hand you might discover something real good!
Good luck
K. Z.