delete any text, email and any other files you arent using. Uninstall any apps you dont use more than twice a week. As long as you dont reset the device, the Market will keep a list of all apps youve downloaded so if you need an app you can access it quickly from the My Apps part of the Market. Even if the app is moved to the SD card it is still taking up some internal memory space. One of the major benefits of root is being able to remove apps you dont need/use or flash a different ROM that has everything trimmed down.