[turbotalon1g]

You can by way of jailbreaking. For ringtones, you can select what song you want and if you right click and go to the info tab (IIRC) there is a part where you can select a start and stop time, you do this hit ok and then right click again and create a new copy/aac version.

Rename this new file to the extension .m4r and then put it into a new folder "ringtones" maybe then you can sync it that way for your ringtones.

This is based on the 3GS since that is what I have, I think the 4 is a little bit better with customization.