Syncme:
Brilliant syncing over wifi app. Easy and quick to setup and its quiet fast, sync'd about 5 gigs in around 30 min, its not usb cable speeds but hey the fact that its over wifi and easy makes up for that. You can also set whether to copy from pc to device only and vice versa or just to pc/device. You can also set times when it should sync.
VLCDIRECT:
One of the best apps I have used, allows you to stream over wifi, I have my hard drive connected to my router and I can browse the list of movies and stream it to my laptop which is connected to my tv. Little bit difficult to setup tho