The length and intensity of light is what triggers the hormones in hens to start the laying process.. If you are able to, you can artificially light your coop so your hens get about 14-16 hours of bright light a day and 8-10 of dark or dim light. Make sure you keep a regular schedule. Hens can stress out it they know the lights go off at "x" time and they dont go off until you get home late after dinner and a movie.. Timers are pretty cheap and a great way to solve that problem.
Other factors for not laying could be stress (predators, mean roosters, wacky schedules with lighting, poor nutrition, all kinds of things) and temperature.. if its too cold many hens just wont lay. you can artificially heat your coop too.. I made a solar heater out of old aluminum cans and a solar fan.. super cheep cheep!
Good luck!
edited to add:
Perhaps I should say ( so you know im not blowing smoke up your tail feathers) that I read about day length and light intesity in a book.. I believe it was Raising Chickens for Dummies.. Kimberly Willis; breeder and enthusiast and Rob Ludlow; Owner of Backyardchickens.com
So perhaps there is no merit to it... perhaps there is.. Of course hens who do not get artificial lighting are still going to lay.. its a matter of when. I doubt they candle lit coops back in the day and the chicken has seemed to continue through time so artificial lighting is not necessary unless you want to lengthen the day and hold off the slowing down of egg production. I did not mean to say that lighting is the only factor to help your hens along or even the correct answer to your waiting blues..