Between iCloud, Dropbox, Instapaper, and all the other cloud services available, keeping the data on your iPad up-to-date isn't difficult. But updating your apps, iBooks, photos, movies, and podcasts still requires you to plug in by default. Here's how to use iOS 5's WiFi syncing to update your iPad automatically.
Turning on WiFi sync is simple. To start, make sure you have iOS 5 on your iPad, and are running iTunes 10.5 or later. Plug in your iPad, and select it in iTunes' Device list on the left. In the Summary tab, check the box marked Sync with this iPad over Wi-Fi.
Your iPad will sync with iTunes automatically, as long as a few requirements are met. To start syncing, your iPad will have to be connected to a power source (you're now syncing over WiFi, but it's not truly wireless—more on that in a bit). But as long as iTunes is running on your desktop computer, and both the iPad and computer are connected to the same network, your device should start to sync automatically every time you connect it to a power source.
If you want to truly go wireless and skip the power requirement you can, but you'll have to do it manually. Make sure your battery isn't on fumes first—running out of power halfway through a sync could cause problems with your apps or your device, requiring a lengthy Restore. Trigger a manual WiFi sync in Settings > General > iTunes Wi-Fi Sync.