Drymax or Coolmax material socks should be good for indoor running. Asics Coolmax models are good and well priced.
In general, for that type of running, you want a moisture wicking sock with no thick seams. Most people prefer them on the thin side, but that is more of a personal choice. Stay away from cotton socks. You want a blend or synthetic type of material. No thick toe seams is also a good rule for any socks.