Check out cell phone mounts. Pro-fit makes excellent mounting kits for phones that will work with all sorts of other things too.
I am trying to find a holder for my car that I like. I have purchased two different one's that connect to the vent, which is a good height and seems to work good except after it's in there a while the part that holds onto the vent tends to "strech" and the mp3 player flops around more. I don't know if it's bec of the weight or what, but it's annoying! Does anyone have any suggestions on a different option or anything??? I'm up for some help here!