You can move many apps from the phone's internal storage to the SD card. You have to do it one app at a time. Start from the Home Screen, then Menu > Settings > Applications > Manage applications. Tap All. Once the list populates, you might want to do Menu > Sort by size to see what are the largest ones. Then tap any app and see if has the option to Move to USB storage. Some apps (especially pre-installed and system-related apps) do not have this option. But the ones that do can be moved to the SB card this way.
Photos and videos that you take should be stored on the SD card automatically.