Again the for the same reason I don't wear sneakers with my kilt I don't wear ankle lenght socks (Just doesn't look right to me). I usually wear socks like these when I'm dressed casually:
http://www.llbean.com/webapp/wcs/sto...=pp&feat=dp474

I'm not endorsing LLBean (I think these prices are rediculous), it's just the first example I found on the web of what I usually wear. I have pairs in green, brown, black, grey, tan and blue.

Adam