Switching from MTB to Road, need buying advice.

Z06C5R

I've been a casual mountain biker for many years now. Never been really serious about it, but I always enjoy going fast on 2 wheels.

Recently however, I've traded the trails at home for the streets and otherwise smooth surfaces on campus. After a week, I concluded I couldn't deal with walking, (It's so darn slow, and boring!) so I brought out my MTB, (Diamondback Coil SS full suspension, semi-downhill type deal). It works fine and cuts down plenty on travel time, but I know it's not exactly efficient in this environment.

Therefore, I've decided to look into switching over to road bikes from mtb. Of course all my experience is with the mountain-end of the spectrum, so I'm not really sure of what to look for in a road bike. I'd like something that's pretty light and built mainly for speed, but that sort of criteria seems to drive what seems like an already high price average through the roof. While the crazy-light carbon fiber race bikes are obviously for hardcore folk, it seems that anything on the cheap end of the scale kind-of lacks that race-bike feel. Is there some kind of middle ground? And then there's the issue of the switch in riding style - I assume when it all boils down, riding a bike is riding a bike no matter how you look at it, but is there something to the more advanced bikes that might throw me off? I'd like to think I don't need a "beginner's" bike, but what do I know?

I think the biggest issue here is going to be price. Think college student budget... Anything anywhere near $1k or more is out of the question for sure - probably $600 absolute max. I'm open to going used to get more bike for my money, if it's possible. I'm not currently planning on becoming a hardcore bike racer, but I'd like to have a fairly nice bike in case I find I absolutely love riding road bikes.

So... Bearing ALL that in mind, (sorry 'bout the long-winded post) is there any particular models or options or anything I should put on my short list? Tips for searching... Anything that would help me narrow my searches down would be greatly appreciated.

Thanks!