Off the top of my head...
Apps...
Various free apps: iPlayer, ITV Player, 4oD, Demand Five, TV Catchup, Netflix, Facebook, Twitter, BBC News, Sky News, Channel 4 News, Dropbox, Sky Go, Sky+, Skype...
Some paid ones: Pages, Keynote, Numbers, iMovie, Garageband, iPhoto, AirPlayer, AVPlayerHD, iCab Mobile...
Games: Jetpack Joyride, Temple Run, Superbrothers: Sword & Sworcery EP, World of Goo, Infinity Blade 1 & 2, Sonic 4 Episode 1, GTA 3, GTA Chinatown Wars, Real Racing 2, Lost Winds, Galaxy on Fire 2...
Some of those games are universal apps, some are "HD" versions specifically for the iPad.