Syncing iPhone with multiple computers?

[EpicInUtah]

So, I went from Droid X2 to iPhone 4. When I did this, I was at work, I just dragged all my music off my Droid SD card onto my work computer, installed iTunes, then synced and set up my iPhone with my iTunes at work. So, all my music is on my iTunes at work...how the heck do I transfer all my songs from my iPhone onto my computer at home so that I can set up my computer at home to be my main iTunes computer so I can do restores, etc without losing my music, photos, etc?
I can't find this anywhere, it has to be an easy fix.
PLEASE HELP!

 

[cdbeshore]

I have mine set up to sync photos, contacts and apps on one Mac with music and video coming from the other. You have to sync with one, disconnect and sync the other stuff with the other. It shouldn't delete what you have on there. Not sure at the present how to download from your current iPhone to your computer, but google around and see if any of the transfer apps are up to date to support the current versions.