Q: What is the easiest way in which to transfer the apps that I have on my existing iPhone 3GS to an iPad?
A: The simplest way to do this is via your iTunes library. Ordinarily when you sync with iTunes anything you’ve purchased, including apps, is automatically transferred from your device back to your iTunes library, provided your computer is authorized for the same iTunes Store account(s) used to purchase the items.
If your computer has not been authorized for the appropriate iTunes Store accounts you can manually do this by selecting Store, Authorize Computer from the iTunes menu and then entering your iTunes Store username and password. You cana lso initiate a manual transfer of purchased items back from your device by connecting it to your computer and then right-clicking on it in the iTunes Devices listing and choosing Transfer Purchases.
Once your apps are in your iTunes library you can simply sync them over to your iPad in the same way as you would with your iPhone—connect the iPad, select the “Apps” tab and choose which apps you want to transfer to your iPad.
If you’re not near your computer you can also simply repurchase the apps on the iPad using the same iTunes Store account. Unlike media content, Apple allows you to freely re-download any apps you’ve already purchased.
Note that neither of these methods will actually transfer any of your application data to your iPad, only the apps themselves will be installed. If you have apps that sync data with an online service or desktop counterpart you can of course resync that data to the iPad in the normal manner.