I have had crazy insomnia since about age 2. For most part, except for getting up to pee 8 times a night, I am sleeping better than I ever have in my life without drugs.
Things that have helped me in the past:
Covering the clock ( this was mentioned, but is worth repeating. Sometimes just removing yourself from the constant idea of "what time is it?" can have a relaxing effect. Also depending on the color temperature of your clock light, the light itself could be keeping you up)
Music: Also mentioned, but one of the things an old shrink told me was to make sure it's the same music every time and that it is only associated with sleep. You're basically training yourself (just like you would an infant) to respond to this sound as "time to sleep". Things with words can be problematic unless you have the ability to tune them out, but words tend to keep us awake because part of our brain is trying to figure out what the words are.
Relaxation techniques: The one where you start at your toes and relax each muscle of your body one by one. This is a big hit for me and is also an exercise for getting ready for labor, so double whammy with that one. Sometimes just the act of concentrating and allowing your body to totally relax is enough for it to let go and allow sleep to sneak in.
Don't use the bed for anything but sleeping: No tv, reading, etc. Obviously doing the deed is cool, but it's a matter of associating the bed with sleep only, as opposed to using it as a place to chill out in.
Dark, dark room: Make the room as dark as possible. If you must have light, keep out of the blue spectrum. All the same things that go with helping a baby go to sleep work on us too, because it's all instinctive reactions.
I know some of you probably know all this stuff and a lot of not sleeping in pregnancy is just not being able to be comfortable, but sometimes just one extra change can make sleeping so much easier.