Do your guy mates have any girls as friends? You could get them to introduce you and hang around in a crowd, probably less intimidating than on your own with a girl. Otherwise, try to put yourself in situations where you'd meet girls - university/school clubs, church/temple/mosque etc or 'religious' social events, orchestras, anything really. Put on a DVD evening at your house and drag some girl mates of your mates along.
Girls aren't that scary, I promise! (well, I can't speak for all of them of course, but I've not known any of my friends eat guys alive...). Don't spring a 'will you go out with me?' on the girl you like. Try to get chatting with her about some mutaul interest, build a friendship over time so you each feel comfortable with each other, then I expect it'll be easier for you to talk to her. You might also get to know her friends or can have your mates make subtle enquiries as to her feelings about you.