In my limited experience (running since December) I am a HUGE fan of Thorlo running socks. They're thick in the toe pad and heel area, but medium weight elsewhere. As long as I wash and dry them inside out to keep the fluff going they're great!  I have yet to find something that works or holds up as well. I definitely had issues with hot spots on the balls of my feet and heels. These have definitely helped. However, my husband, who is not a runner, just discovered that I keep the "good" socks for running and I appear to be losing my supply :-)

I like medium thickness socks...not too thick (like Thorlos) but not too thin (like some of the friction reduction socks).  I have found the perfect sock (for me at least):

They are pricey ($9.95 USD) but worth it to me (I own 3 pair...I try to ration them out throughout the week ) Here is the link if anyone's interested.