Homemade Laundry Detergent: 1 cup Borax, 1 cup Washing Soda, 1 bar of Fels Napa, Ivory, or Zoot soap. Grate soap and mix with other ingredients. Use 1 tablespoon per load (your water quality may require more or less, as well as how soiled the load is!)
Homemade Dishwasher Soap: 1/2 cup Borax, 1/2 cup Washing Soda, 1/4 cup Citric Acid (some add a bit of salt, too). Mix together and store. Use 1 teaspoon in main wash compartment, 1/2 teaspoon in pre-wash (your water quality may require more or less). Use Vinegar as a rinse.
Homemade All-Purpose Cleaner: 1:1 ratio of Vinegar and Water. Works on tables, counters, floors, and windows.
Easy Disinfectant: Use Hydrogen Peroxide for a quick bathroom cleaning solution.
Make Liquid Hand Soap: makes a whole gallon for around $3.50.
Use washcloths instead of paper towels and cloth napkins instead of paper.
Use cloth toilet paper instead of disposable. (Some prefer to use it only for urine, saving disposable toilet paper for the rest.)
Cloth diaper your babies.
Use Baking Soda instead of toothpaste.
Use a mixture of Baking Soda and water as shampoo. Use a mixture of Apple Cider Vinegar and water as conditioner.
Discontinue your cable/satellite and use programs like Netflix, Hulu Plus, or just your computer.
Use cell phones that do not require a monthly plan.
Borrow baby clothes/items from friends or relatives.
In The Kitchen
Plan your meals before you shop and use a detailed list at the store.
Use bagged rice and dry beans.
Buy whole chickens and use it all (meat in various meals, bones for broth).
This list will continue to grow. Have anything to add? Post it in the comments.