Sometimes the best way to alleviate our fears is to actually face them.
I think that since you have identified being around people as being something you feel uncomfortable about that you should make it a pnt to place yourself amongst them at any given opportunity you can until you are able to overcome your fears.
Start out by going to where people are in different environments. Start out with something like the mall. Go shopping for something that interests you. While standing in line to pay make it a point to talk to somebody standing in line with you. Even if it is just to ask what time it is or to comment on the item they are buying.....think of something that you can talk about that will elicit some type of response from them. If the item they are purchasing is something you know something about say some thing like..."Oh, I see that you are buying that cellphone. I have the same model and I absloutely love it!!" Or if its a book, say something like..."Oh I can't help but notice that you're reading James Patterson....I read his last book $$$$$$ and I really enjoyed it!!!" As a first exercise this will warm you up to being comfortable with intiating a conversation with somebody and even if it doesn't get very far it will increase your confidence as you see others respond. After paying for your item or they have paid for theirs smile and wish them a good day.
Next time try changing the environment to a grocery store, pet store, library and try doing the same thing. Sign up for a course or hobby of interest where you will meet others with smilar interests. As the others have suggested...tune into listening and look for opportunities to make comment showing others that you are genuinely interested in what they have to say.
Make it a point to master this in the sense of overcoming your fear. Once you do you will look back on it as we all do once we see things as a risk well worth taking.
Good luck ~ Goody