There are many ways to find out. Have you tried performing you songs at open mic events?
If you get stage fright, I would suggest youtube.com. Upload videos of yourself singing your songs. Make sure all your material has copyrights of course and are registered through (ASCAP,BMI, SESAC) before doing any of this. There's also www.myspace.com.
I read uPlaya can actually detect whether or not a new style and trend of music is going to be successful before it happens. www.uPlaya.com
