- Twitter (Free) — The official Twitter app allows fast app switching, and even sends tweets when you've switched out of the app, including photos and video.
- I Am T-Pain ($1) — Now, in iOS 4, you can share your recordings with friends on Twitter, Facebook, YouTube, or email, and also record video when used for the iPhone 3GS and iPhone 4!
- Pandora (Free) — Play your tunes in the background!
To see the rest of the list, just keep reading.
- Windows Live Messenger (Free) — This just-released app is primped and primed for iOS 4 with its quick switching capabilities, and keeps you signed in when in the background.
- Evernote (Free) — This app will continue recording your notes in the background, and is Retina display-ready.
- FlightTrack Pro ($10) — Always on the move? This newly updated app will allow you to sync the flights you're tracking with your calendar, and send SMS messages within the app.
- New York Times (Free) — The NYT app has been upgraded to be more stable, and allows for fast app switching.
- TripJournal ($1) — Track your trips with this app, which uses GPS to plot movements along your route, add bookmarks and notes to certain locations, and geo-tag your videos and pics for easy reference.
- LinkedIn (Free) — Fast app switching allows you to quickly move in and out of LinkedIn.