Another main idea I've found to save money is "buy used". This includes everything! From cars, appliances to household goods.
Places like thrift shops, Goodwill, Salvation Army, etc. have amazing bargains. Until you explore some of these places, you don't know how much you're missing. It is best to be an educated consumer, to know what is a treasure find versus "junk", and it's even fun!
Check classified ads and yard sales as well. The key factor here is planning though (as Teg stated previously). Know what you're looking for. Do not just "shop".
Teg, I can't second strongly enough the key item of budgeting. A good budget is critical to financial security and happiness. There are many good software packages that are free out there. I recommend going to
www.about.com/finance and doing a search. They list some of the best free packages.
Again, great thread Teg, can't wait to see other hints from everyone!