I second the hybrid idea. I got a Gary Fisher Nirvana about four years ago for this purpose and am really glad I did. It handles the occasional sand and gravel much better than a dedicated road bike, and is geared better and has a better riding position for speed than a mountain bike.
When I was looking everyone tried to wow me with disc brakes. Once I tried them I was amazed at how much they sucked. They seem dangerous to put on bikes. They are a solely gimick in my opinion. I think the only place they belong is on a mountain bike that plans to encounter mud. Unless you are going through mud, which can make pads on your rim slip, they are not an improvement. Having traditional brake pads further from the axle gives them more torque on the wheel, so you get better braking force than with something acting so close to the center of the wheel.
When I was looking four years ago there weren't any great new brands. Trek, specialized, Gary Fisher, etc... are still good. If you have an REI near you, they have their own line of bikes that are of decent quality and a great value for the price. Whenever I get my dividend I am tempted to get one. Haven't yet though.
Good luck.
