What's A Girl To Do!?!

Here's the deal, I am in my mid-20's and I feel like my life is just passing by.  I feel this is the part of my life that I should really be enjoying, that I should be living.  I thought that by this point in my life I would have met someone and be in a relationship.  Yet here I am single as ever.  I can't even remember the last time that I met a guy that I liked, led alone one that I wanted to date.  And the guys that I have wanted to date always seem to cast me into the "friend" category or "she's like a sister".  When will guys learn that most girls do not want to be placed into those categories.  Where am I going wrong that has put me in the position that I am in.  Why am I appealing enough to be their friend, but not appealing enough to be more than that?  How do I get out of it?  Am I my own worst enemy?  And where can I go to meet a decent guy.  In the past I had always met people at school.  Since graduating, I have found it difficult to meet new people.  The problem is that I don't know where I could go and hang out to meet someone; to be able to strike up a conversation, for a guy to approach me.  It has come to the point that I have even considered using an online dating service.  But I much rather meet someone in person.  I have this idea or dream of how I would like my life to play out, but I know that it's not very realistic.  So what is a girl to do?