here's a nice summary of the different types:
http://www.createforless.com/buying-...right-one.aspx
Choosing your batting depends on how heavy you want it to be, how much loft you want, how closely you want to quilt, whether you want it to be washable, etc. Also keep in mind that if you use white fabric you want to use white batting so it doesn't show through and dull the look of the fabric. The web sites for the various batting manufacturers also describe their uses, etc. My quilting instructor mostly recommends Hobbs 80/20 (80%cotton,20%polyester) as a good basic batting.