How do you meet pilots looking for passengers?
Aviation, for me, is a lifestyle more than anything.  

Some background: I'm still a college student, but I'm going into the Air Force, I am on my school's flight team, I am getting a degree in asto engineering (and astro physics).  Almost everyone I know is involved in aviation or space in one way or another.  We fly around the southwest part of the country all the time, but it's normal.  One weekend I'll fly LA, and another a friend will take us to Vegas.  

Have you considered going to flight training, yourself?  If you find a good flight school, you wont only learn to fly yourself, but you will meet other people like you.  And once you become friends with them you can all fly each other after you get your licences.  

Honestly, I would be pretty uncomfortable flying with someone I don't know next to me.  For example, If you've ever picked up a hitch-hiker you might know how it's a bit awkward and uncomfortable making small talk with a completely random person.  Now imagine what that would be like in an airplane... a plane that most likely has controls in both (front) seats, and could do serious damage if used improperly.