5 of 10Image
Ultimate Rotation (7-day free trial available)
For those who don't want to root the Nexus 7 or even install a replacement launcher, Ultimate Rotation allows rotating the home screen (and other functions) using the standard Nexus 7 Jelly Bean launcher.
Here's the last home screen rotated into landscape.
I am a heavy Evernote user and the app works well on the Nexus 7. The most recent version takes full advantage of the larger tablet display with sliding panes as demonstrated in this screen.
Plume (free and paid version)
I am a heavy Twitter user and Plume is my preferred method to interact with the social network on the Nexus 7.
The app displays a single column timeline in portrait, but when you rotate into landscape it presents three columns of the user's choosing.