iTunes won’t let you sync the same content with more than one computer. However, you can sync different content with different computers. For example, you could set up your computer at home to only sync your music and videos in iTunes. You can then set up your work computer to only sync your contacts and calendar in iTunes. Maybe set up your laptop to only sync photos. This way, you can fill up your device with content from different places.
In order for this to work, connect your device to your computer and open iTunes. Click on your device under Devices on the left side of the iTunes window and then click on Summary tab. Make sure to check the “Manually manage music and videos” option. This will allow you to sync your contacts, calendar appointmets, etc. with different computers without having to delete your music and video content from your device.