You've got an iPhone 4 and want to use FaceTime, but don't have a WiFi connection. What to do now? Well, you can download the newly-updated Fring App (Free) and video chat all you want since it now allows video calling over 3G on any phone, by taking advantage of front-facing cameras (like the one on the EVO 4G).
Take note that chatting over 3G will impact your data usage (unlike the FaceTime feature), so be sure to monitor how much data you're pulling down each month. Fring is available in the Android Market as well, so gather up your Droid-loving friends and start chatting!