I would use headphones too.
IMO ignoring them is a mistake.
Look around at all of the people using Ipods. They don't have bookshelf speakers strapped to their heads.
Headphones are very good to reference your mix with.
Should you mix with them? Probably not, but if your room is poo, and most likely your dorm will be, then headphones might be a usfull mixing tool along side low volume speaker mixing.
An argument can be made that mixing in headphones is better than doing so in a poor acoustic enviornment with speakers.
This is surely debatable, but plausable.
Anyway
Grado sr60's are generally considered miles ahead of similarly priced headphones at their price point.
They don't isolate well.......well not at all really. They are very open, so if you need closed cans look elsewhere.
For closed cans under $100 Audio Technia ath m50's are the name I hear being brought up the most anymore.
If you don't feel like dropping so much on cans, JVC HA RX700's are highly recomended at their price point at head-fi.org.
Just picked up some myself. Impressive for $34 shipped, and resolve a nice amount of detail.
Distortion from poorly mixed/mastered music is easily flagged with these.
At the same time they have a good full sound.