We're having a lot of trouble getting my two year old son to fall asleeep at night. My wife and I work out of our house, so the child doesn't have to get up in the morning. We're tried everything . . . early naps, no naps, shorter naps, waking up early, waking up late. Nothing works. Suggestions? We now have to get him up two days a week for pre school. He's cranky. We're sure its because he's tired. Are there sleep medications for little ones?

No, no and more no...do not give your child meds to help him sleep.
How long did you try any of the no naps or shorter naps (i found with my kids shorter naps were hard because they didn't want to wake up ealier).
I would try the no naps...for a few weeks. Get him up at the same time (ie before 8 am) every single day whether he has preschool or not. Get him into a routine. You didn't say how long you had tried anything for, but it does take a while to change habits. At first he will be used to going to bed at a certin time so it will be hard (even if he's tired) to get him to bed ealier, but after a few days of no naps he will just be tired and will probably go to sleep ealier.
Don't be temped to try any meds or anything to get him to bed ealier, not only is it dangerous (kids have actually died or become very sick from being given meds to help sleep) and irresponsible it's a terrible habit to get your child into, they need to learn to have healthy sleep patterns (which can takes weeks to change). Just take it slow and relax. Get into a bedtime routine if you don't have one, supper, bath, quiet time (book reading, a cuddle etc), after a certin hour try to get him into the habit of doing quiet activities...coloring, you or his mom read him a story, play with something that doesn't require him to be running around.
I've got a 2 year old who will be up till 11 if she sleeps any later than 3pm....so i don't let her, if they are tired and want a nap you have to try and keep them from having a meltdown, play with them, distract them somehow, have an early supper and put them to bed early.

you can also do a thing called ferberizing your baby. Hopefully I can post this here, its a method of changing schedules, either.. Getting him up an hour earlier every week until he is getting up and going to bed when you want him to, or if he is like my oldest son, you can keep him up later and later until he is getting up and going to bed when you want him too. Like say, he goes to bed at 2am and you want him to go to bed at 8pm. Then you keep him up til 3 for a couple of nights, then til 4 for a couple of nights, then til 5 for a couple of nights, until he is going to bed at 8pm. It takes a while, and you will be exausted trying to do this, but it does work, my son used to go to bed at 3-4am and sleep until 2-3 pm I had to do this, it took about 2-3 weeks, and he has gone to bed at 9pm and gotten up at 8am ever since. I however can not be lax on his schedule, because he easily falls back into the 3-4am routine. I did this when he was 3 years old, and he is almost 8 now.

my son was 2 1/2 when he finally slept through the night. Still have no idea why he would be up screaming all night long. It was horrible. Nothing--I mean NOTHING WORKED
Except time.

I notice that ds gets really funny -- like funny ha ha I'm going to entertain you now, if he gets off schedule. There's a small window of opportunity between 8 and 8:30 and if we don't get him to sleep -- he's bouncing off the walls until 10:30. He goes to day care and the let him nap about 1 1/2 hours. We get him up at 6:45 a.m., but on the weekends our schedule goes out the window and we end up paying big time -- he sleeps in until 7:30 or 8, doesn't go down for a nap until 12:30 and sometimes sleeps 2-3 hours, then he won't go to sleep til late. And sometimes he has a nap around supper time. So, I'd try to get him into a routine. Catch him before he gets to goofy at night. Feed him dinner, give him a bath, let him play a little bit, then rock him and/or read him a book. The bath works wonders.