It's a shame it isn't socially acceptable to do more than have a superficial conversation with people you might meet on the street. I've found people are willing enough to chat, but I don't think I could get up the nerve to actually ask a stranger for a phone number if I was interested in pursuing things further.
I'm in a similar bind to you, Mercutio. I do have a few friends, but I don't really meet anyone new through them. One guy owns a taxi shop and that's pretty much his life. Another one moved to NJ so I don't see him that much, and he was pretty introverted so he really wasn't a good prospect to meet people through. I've lost touch with all my friends from high school, although now I wish I would have made a greater effort to keep in touch. I think meeting people is easier if you have a core group of friends that can help you meet others.
As far as finding love interests, I'm probably the last person to be giving advice in that department since it's been nearly 20 years since I was seriously in love with anybody. I would even try to hit on people I see in the street at this point, but I'm so particular that I've seen maybe a dozen people that I would consider my type, and with my luck that usually happens when I have to be some place and don't have time to chat. As far as my previous love interest, the fact is we were both too young, inhibited, and inexperienced to pursue things further at the time, so it was kind of the classic Greek trajedy(athough I'm Italian and she was Chinese). I'm still trying to find her, if only to be friends. Given that more than half the people I went to high school with never married, I really don't consider this a pointless endeavor. Barring any luck finding her, I would say my best option is to just get up the nerve to start asking for people's numbers after chatting with them, or maybe trying online dating(I've looked on many sites, and haven't seen anything even remotely interesting). I would probably have to say your options are as limited at this point. As far as joining clubs or pursuing common interests, all of the things I'm interested in as hobbies have a nearly 100% male membership, so that's not a option for me as far as meeting a love interest directly. And to be perfectly honest, although I'm always open to the possibility, my life as it is now is just fine one way or the other. I've learned to like myself a long time ago, and hopefully that will come across should I ever meet someone.
As a last word of advice, don't settle for anything less than you want just because you're lonely. I'm sure I could have dated many people these last 20 years, but none of them would have meant to my what my last love did. When you meet the right one, you'll just know it the way you did with Amy and I did with Stephanie.