Night Sky, Tree.
The lower clouds speed past, while the upper clouds drift slowly above. (That's not completely true, of course, the upper clouds are just farther away and only appear to be moving slower.) 20-second exposure and a f-stop of f/3.5 (could have been better).
ON DOWNLOADING THE IMAGE:
Using my Flickr photos causes loading problems (as one can see now thanks to the Dusk image), so for the sake of keeping 0 (yeah, for some reason, I've decided to write it like that, and, yes, I have just enjoyed a piece of cheese. Gouda.) running smoothly, I've decided to use a smaller version above, and provide a link to the original size for anyone that wants to download it. This way, it'll be less stressful on your bandwidth and mine. Note, this only applies when I'm linking to Flickr pictures; I'm using Picasa for the rest.
You can download the full-sized picture here. (It's also available on my Flickr page.)