Bless your heart. I had serious insomnia probs a few months back -- to the point where I got a prescription for it.

But thankfully things worked themselves out and I've been okay for sometime now. Here's some of the things I do. I hope some of them might help you too!
Make sure you're taking your vitamins and supplements EARLY in the day. Vitamins energize the body. Many herbal supplements do as well. If Vit C gives you heartburn, eat an orange -- but don't drink OJ. The fruit itself usually doesn't give you heartburn like the juice will. (Bizarre but true.)
Floradix is good stuff as it's loaded with Vit Bs as well as iron, and that can help provide needed energy and combat nausea. Best to take prior to meals and if you're doing it 2x daily then make sure the second time is before your evening meal, as many hours before bedtime as possible.
Although I haven't had much luck with it in terms of iron yet, I am working on more greens, and cooking in my iron skillets, etc. during the day for my anemia. Have you been tested? That could be a big part of your problem. Do you eat meat? Leafy veggies?
Also take ONLY minerals at night -- never take vitamins at night -- and be sure that your calcium has magnesium (and potassium ideally) in combo with it to help you absorb it better. Calcium carbonate reduces the acid in your stomach but calcium needs some acid for effective absorption so make sure you're getting enough calcium from food sources when you're taking antacids.

Otherwise, take a calcium/mag supplement if possible. It helps your body to relax. And your body will only absorb a set amount of calcium at a time anyway so if you're full up anything extra gets flushed out.
(FYI I've read that you shouldn't take zinc or iron with calcium -- they can interfere with its absorption.)
Eliminate all forms of caffeine from your diet -- including half-cafs and chocolate if you're having severe insomnia. Sorry moosemommy

I hate to say it but any caffeine can affect sleep, period. So using it as an energizer during the day only works for folks who don't have sleeping problems at night. If you don't sleep well, it's best to avoid caffeine. But if you absolutely have to have it, limit it to before noon only. I know that sounds preachy but it's pretty true. (Don't hate me. :P)
I agree that environment plays a huge part in sleeping, too -- I've found I get hot very easily nowadays so I've started wearing less wintry nightclothes, etc. I also get stuffed up easily so have a vaporizer thingy running -- which helps keep me from waking up to sneeze or blow my nose. (AH but I also take Chlor-Trimeton for allergies as needed and that helps a little. That's a personal choice; some folks take Benadryl, some take nothing. It's what you're comfy with and what you need. Obviously if you don't need it, don't take it.)
There are some really good homeopathic remedies for sleeplessness too -- if you're interested, PM me and I'll send you a list.
I totally agree that sound (white noise, CDs, etc.) and surroundings (pillows, blankets) are also important, as is light (do you like light? Total darkness?).
And keep in mind that things which might have worked for comfy sleeping prior to pg may no longer work now. Try something new. You might've always been a total darkness no noise kinda gal but third trimester mama might actually be more comfy with a fan and a nightlight. Who knows?

Don't be afraid to try a new ritual.
Good luck, hope some of that helps and sweet dreams!