The Dorkstorm thread got me thinking - yes, we can all pass judgment on Dungeons and Dragons Players, and giggle at the goths, but what are the hobbies that you think are cool? When you're talking to someone at a party, and they mention that they spent the weekend xyz-ing, and it immediately raises your estimation of that person?
A couple of mine
Music Afficionados - i never have any idea who the Mustard Nancies (not a real band, but you know what i mean) are, but i'm impressed when people are on the cutting edge of music - NOT the current favorite band in rotation on MTV.
Marathoners/Tri-atheletes/Cyclists - Just the dedication it takes to do a marathon or iron man/woman, road races - impresses me.