Join a bunch of clubs, join a sport (even if you're not good at it, just play it), dress nicely (Aeropostale, Hollister, Abercrombie & Fitch, American Eagle) get a clean cut, and trust me people will know who you are and you'll make a lot of friends.
I had the same problem in high school - it wasn't because i was too shy, it was because i didn't really do anything besides tennis. Now I'm in college and I do a bunch of clubs and I'm captain of my tennis team.
Smile, man. you deserve it. Newgrounds should be your cake and ice cream at the end of your day.