Depending upon what country that you are in (and whether they are still in the store) you might be able to re-download them via the Purchased tab in the iTunes store app on your phone. If you are not in a country where music can be re-downloaded then do you have a copy of them on your computer's iTunes or on your backup of your downloads that you can use to resync them ? If not then only iTunes Support could potentially grant you a re-download : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page, then Purchases, Billing & Redemption
You should be able to re-download apps via the Purchased tab in the App Store app, and ibooks via the Purchased tab in the ibookstore in the iBooks app.