I currently get anywhere from 2 to 3 DOZEN eggs a day from my flock, and I'm not using any supplemental lighting in my coop or anything!
I have my own little system that I am slowly perfecting. I keep the bantam eggs for my own household consumption since we don't eat a lot of eggs and I figured nobody would want to pay for little eggs anyway.
For the rest I sort them into two piles, ones that are really yucky (lots of poo, funny color, cracks, etc) I put aside in a bucket on the counter. When I get a decent amount of these collected, I turn them into a big batch of scrambled eggs which I feed back to my chickens for an extra protein boost. I also bake the shells and crush them up to feed back for extra calcium.
All of the 'good' eggs, I collect in one of the veggie drawers of my fridge and I sell them. At first, I only had enough to sell a few dozen a week to people I know at work and I was able to get enough used egg cartons from friends and family to keep up. Now, I am getting so many that I had to order egg cartons from eggboxes.com and I am planning on putting a flyer up on the bulletin board at work to expand to people other than the ones I know personally. I also plan to put up an ad on Craigslist.
I actually bought my chickens mainly as pets and to provide natural fertilizer for my garden, since I don't eat a lot of eggs, but selling the eggs has been a nifty bonus because at $3 a dozen I am making more than enough to cover their feed and I might even be able to put a little extra aside for expansion projects (like a nice incubator).