Step one for us was to get new wallets that had two bill compartments- one for cash, one for receipts. I got a Big Skinny and DH got an ALL-ETT.
Then I got one of those plastic file dealies, you know, with the rubber band that loops around a button on the front. It was $4 at Office Max.
We save our receipts in our wallets, and then, when they get full, once a week or so, we put them in the plastic file. The current month is always the front pocket. Around the first of the month, I sit down with a calculator and some paper clips. I organize them into four categories: Food, Non Food Consumables, Durable Goods, and Gas. The difference between Non Food Consumables and Durable Goods is, "Do we A) use this up or B) wear it out?" A = NFC, B = DG. I define food the way the state does- if it's untaxed, then it's food. (So beer is NFC.) This whole thing takes me about 15-30 minutes. I usually add up what we've spent in each category, and write the total, category and the month on the front receipt. Then I stick all the paper clipped piles in a back pocket of the folder.
At tax time, I send them to our accountant (wonderful SIL), who uses them to get us a better tax return. I usually write down totals on the dossier that we keep our tax copies in, i.e., "In 2009 we spent $2186 on gasoline, $2876 on food, blahblahblah."
What's nice about this is that I know just where our money is going, and if we need to return anything, I can almost always find the receipt in five minutes.