A non-suspension hybrid will suit most of those needs. Many of the "mountain" bikes you see on the road are cheap department store bikes that you wouldn't actually want to take on a trail.
Not sure what you mean by stylish. Everyone has their own opinion on that.
Aluminum isn't necessarily harsh - it depends on the tubing shapes and sizes. If you want "light" you pretty much have to have aluminum, unless you go for something like a "fixie" or a road bike, which will limit your trail useage.
The Kona Dew Plus is a pretty good deal:
http://www.konaworld.com/dew_plus.cfm
You don't mention your gender, but they also make a step-through with disc brakes, a real plus in my books.
http://www.konaworld.com/coco.cfm
The Giant Escape City comes complete with racks and fenders:
http://www.giant-bicycles.com/en-us/...y/11500/55828/
As does the Jamis Commuter series:
http://www.myjamis.com/SSP%20Applica...cat_grp=strt_1
There are a ton of bikes out there that would work and be in or under your budget. You really need to test ride a few and decide which one feels best. Don't forget to budget for things like a helmet and bags to carry stuff as well.