The Envelope System--for budgeting your paychecks and staying on budget. This was actually how I saved up $630 for a computer and $350 for a new aquarium at the same time... then I stopped doing it. Maybe I should start again.
"Spend Less on Groceries by Shopping the Weeks you don't get paid" - so very true. I tend to buy ONLY the essentials when I'm shopping with a lighter bank account (buying only essentials and dusting off things in my cupboard).