Originally Posted by ZR_Yancy
Yes you can download it again for free. You have to download it in iTunes. If you do it through your phone, you'll have to pay again.
Wrong. Go into the App Store on your iPhone, and select the app you already purchased and want to reinstall. You have to click the button that says "Buy" and put in your iTunes account password, but once you return to the springboard, you'll get a message informing you, you have already purchased this item and can download it for free.
Hope this helps.