My "everyday coupons," the ones I take to the stores with me, are in an accordian folder with lots of categories. This works for me because I don't have to flip through a large pile of coupons if I find an unexpected/unadvertised sale in the store. I forget where I found the category list originally, and I have modified it to meet my needs, but here's the list:
Baby items
Baking items
Beverages
Bread/rolls
Candy
Canned goods
Cat food
Cereals
Cheeses
Cleaning Products
Dairy Products (considering a separate one for yogurt)
Frozen items
Hair Care Products
Laundry Supplies
Meat
Medicine
Miscellaneous
Paper/Plastic Products
Pasta/Rice
Personal Hygiene Items
Oral Care
Produce -- not canned
Snacks
Soap

All my other coupons for trades, coupon trains, and the I-didn't-think-I'd-ever-get-this-but-it's-free sales stay at home organized alphabetically in an old baby wipes container.

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~Jeweled

I use a binder, with trading cards and photo pages to hold my coupons. I also have dividers to seperate different sections 1st is Commissary since I usually have a few "military store only" coupons. In the next section I have my coupons divided by Baking Supplies, Breakfast, Condiments, Canned Foods, Dry Goods, Meat, Refrigerated, Frozen. In the next section I have non food items such as bodywash, lotion, deoderant, razors, cleaners, storage containers. The last section is pets.

I used to use an accordian style folder and then switched to the binder. LOVE it and it's so much easier to take through the stores because I don't have to rifle through tons of coupons. I can just flip a page and pull out what I want/need to use.