I have tried lots of apps on tablets. I recommend the followings:
File Manager
GrooVe IP (google voice phone call)
Google Voice (check google voice inbox and send SMS from tablet)
ezPDF reader (best pdf viewer)
PowerAMP (music player)
TuneIn Radio Pro (thousands of free online radio)
NetFlix (on-demand movie and TV)
Camera Zoom FX (taking pictures)
PPTV (best Chinese media content)
Dopool TV (chinese TV, not so good as PPTV, but a good alternative)
Yelp/Trip Advisor
Weather Bug
ColorDict (best dictionary)
Kindle
Nook