Dimensions of EACH cabinet.
Well-lit pictures, not snapped by a cell phone in a dark garage.
Make sure the color on the computer screen resembles the cabinets, even if you have to color-correct it.

CL has a limit on the number of photos you can upload, BUT you can link in photos from PhotoBucket or elsewhere.

All the above and...
If you want less hassle you have to be realistic about your starting price or the nuts will come in droves. If your cabinets are outdated but all wood bring the wood box quality to attention. Basically sell on the parts that would appeal to people today without getting weird about it. If the door style is a popular style but an outdated color bring up the idea of how beautiful they would look painted if one didn't like the color...a new kitchen at such an affordable price! If you have already taken the cabinets down, try to add a picture of the cabinets when on the wall. A large majority of people want a lot for nothing and have no imagination, plus you are competing with some great deals on cheap new cabinetry with less hassle. I have sold a few things on Craigslist, it takes a little more time than a garage sale and you get a little more money. Usually (but not always)on non antique or collector furniture or cabinetry you are looking at around 1/4 of the real "new" when you first bought the product. There are a few exceptions to this if the item is perfect and incredible.

If you know people in your neighborhood you might mention they are for sale...sometimes they are great to install in a garage.

Here's what I looked for/asked for when I looked at cabinets on craigslist. As others already said: good pics.
The dimensions of each cabinet... break down and give sub headings for wall cabs and base cabs
Give the type of wood
Age of cabinets
Closeup pic to "highlight" good points (ie: finish, moulding, interior hardware,)
Be realistic about price. It's craigslist. People shop there for a good deal. Your items are typically not worth what you think they should be.

remodelfla, you may have read my rants on "How to price your used furniture" on craigslist last year.

Great ideas! . . . and if all that fails . . . the Habitat for Humanity in many communities have a store (ReStore) where they sell donated items (including cabinets & countertops, etc.) as a fund raiser. We donated our cabinets, Corian countertops, kitchen sink, faucet, light fixture. They picked them up & were wonderful to work with. It was very nice to know that someone was able to benefit from our remodel & the items were not going into the land fill.

Good luck!

Careful with Craig's List... I got a lot of sketchy emails about wiring money... you're better off to sell them on ebay or at a garage sale. Just be careful with Craig's list.

True about the fraud end of things...never take cheques, cash only. You might also decide on your price and state, FIRM in the offer. Then there's no back and forth. I sold mine easily on KIJIJI (canadian) to the first guy in the door and had 3 people in line. I think b/c I priced well and had completely decluttered etc. I may have lost a few bucks but less hassle and they came to pick them up!! Good luck!