http://elijah.pinoguin.com/blog/blog-view/article/sync-treo-650-on-ubuntu-linux.html

This link should get you there, but I'll find time to have a graphical walk through the Centro and Ubuntu 8.04 Hardy Heron.

Don't forget to restart the bluetooth service. Also click on the bluetooth icon in the notifier and don't forget to enable network services.

Not as fast as USB sync, but definitely less troublesome without the wires.