I have a few compilations that I mostly listen to late at night. One of them is the first FAX compilation, a double CD of ambient electronic music from one of the most prominent ambient labels of the mid-90's. The second is a promo I was given of a compilation called United States of Ambience 2, which is pretty much what it sounds like.
I've got two tracks today, good for when you realize it's about 1:30 or 2 in the morning and you've been up for longer than you expected but aren't quite ready to go to bed yet. Maybe you've got the last of a glass of wine to finish, maybe you're on the last few pages of your book (or maybe, with pleasant synchronicity, both). Or maybe other people don't sit up all night reading and listening to ambient music and drinking wine.
They're both beat-driven, but quietly so. They don't pound, they throb and pulse. They're subtly insistent, taking you with them while they go somewhere and look around and then bring you home again. The first, "Electro Dreams," is a brisk walk at night, past people moving through their own lives and doing whatever it is they need to do separately from any observer and from one another, while the second, "Introspection Part 1," is a look around the cannery sometime in the very early morning when even the people at work are asleep on their feet, dreaming themselves into the machinery in a way the daytime workers never experience.
Both of these appear to be out of print. If you find them in the used bins or feel like dropping the 7 bucks Amazon sellers seem to want for the first Fax compilation, I'd say go for it.
Zenith - Electro Dreams (FAX Compilation)
Salt Tank - Introspection Part 1 (United States of Ambience 2)