Canonet

You have a number of options:

1. A road bike with drop bars: either a racing bike (probably impractical), or a touring bike (can carry lots of stuff), but is a little slower and heavier than a racing bike) or a cyclo-cross style bike like the Surly Cross-Check which you can tweak to make either more road-biased or more trail-biased. Racing bikes generally aren't going to accept disc brakes; tourers and cross bikes often can. They can also take wider tires, fenders and racks. You lose some speed with the increased weight, but you gain versatility and toughness with cross-style bikes and tourers.

This option will probably start at about 700 dollars new.

2. A hybrid: most likely a "performance" hybrid with 700C wheels if you like to go faster. Many will be able to accept wider tires, fenders and racks (but some may not; check). The disadvantage is that you lose some of the riding hand positions, and these bikes are generally as heavy as (or heavier than) tourers and cross-style bikes. Componentry may be (but doesn't necessarily have to be) of a lower quality than road bikes.

This option (for reasonable quality) will probably start at about 500 new.

My advice is to ride as many options as you can and see how you feel on each. The more comfortable a bike is, the more you'll ride it. Then, once you've narrowed down the type, go test ride four or five different manufacturers' products at your price point.

I know this probably isn't as specific as you hope ... the trouble is, I can recommend something, but deep down, all I would be doing is telling you what works for me. There are as many opinions on what constitutes the perfect commuter as there are commuters.