By right-clicking (or command > click) on your iPhone's icon in iTunes, you'll see the option to "Transfer Purchases." Selecting that option will move all of your iPhone-purchased apps to your iTunes library. This works great if you haven't yet set your apps to sync with iTunes, or, as in PetSugar's case, she had her computer serviced by Apple, which wiped her iTunes library clean. Note that in order to move the apps over to the library, you'll need to be using an "authorized device" — no sharing apps among friends! Once you transfer all your purchases over, you can then sync your apps, and all the hard work will be done for you!