If you have those nights, here's a list of a few websites I've found particularly helpful for passing the grueling overnight hours:
1. A Soft Murmur - Terrific site for ambient noise like rain and crickets.
2. Primitive Technology - There's something incredibly peaceful about this chill guy in the forest building his own habitat, weaving his own baskets and making his own sandals - all without a word or a modern tool in sight.
3. Storium - Storium is an online creative writing game. Each story is a world, and every world has a narrator (aka game master). It has a set of pre-built templates (in a variety of genres) that serve as a customizable jumping-off point, or you can use them as-is. If you enjoy a good RPG, this might just be the time-passer for you.
4. 100,000 Stars - This is an interactive 3D visualization of the stellar neighborhood, including over 100000 nearby stars. Created for the Google Chrome web browser, but it worked fine on Mozilla for me.
5. NoSleep (Reddit) - I saved this for last because it's only for those who really aren't trying to get back to sleep. The scary stories are hit or miss, so sort by "Top" and spend the next several weeks being startled by every creak in the night.
Long-term insomnia is no laughing matter - our bodies need sleep and the lack thereof can bring on a world of other physical and mental problems, so see a doctor is this is more than just an occasional thing for you. Or hit up your favorite blogger on Twitter or Facebook so she can commiserate.