I'm not going to reiterate my infamous, "He's Just Not That Into You," post, although you can review the entry if you wish - it comes highly recommended.
What I am going to say is that just because a man isn't that into you now doesn't mean he never will be.
Doesn't it seem like just when we give up on a guy, *poof*, there he is asking us out? I don't prefer the route of sitting around wistfully desiring him whilst passing up other opportunities, which is why I tout to get off your duff and go be with your friends, develop your talents, make yourself busy and happy - all those things make you even more desirable.
We all have friends who, in the back of our minds think, "If he/she were ever interested, I'd definitely give that a shot." I know that I've dated a handful of dear friends and they've turned into amazing experiences.
If you find yourself lamenting over some hunkalicious man-friend or babealicious confidante, don't fret! Buck up, keep your eyes to new situations, keep your options open, be the best you you can be, and you never can tell...
What I'm saying is, don't pin all your hopes and dreams on one person who is not yet into you, but don't totally write that person off just because they haven't yet realized what a fabulous romantical partner you are.