iSync isn't going to work for me. What will???

I'm a recent switcher. Maybe 6 weeks or so. I've been using Yahoo for all of my email purposes along with it's address book. The printing options in Yahoo, well, pretty much suck. The printing options in the Mac address book are awesome. However, I need to keep the address book in an iMac and iBook in sync with one another. Normally this would be simple enough using a .Mac account. The problem is though I'm having to use custom fields for my contacts and .Mac will not allow that. Customer service confirmed this. So, what's the best way? I'll still be using my Yahoo account as my mail server. They have intella sync but... you guessed it, Windows only. The only option I can think of is to "back up", which I would do anyway, say, the iMac to an external drive, or what ever, and retrieve the address info with the iBook, or visa versa.

Any takers???

Thanks in advance,
Jason