How can I do usb tethering with Mac Os X (using gingerbread Acer Liquid Metal & snow leopard)?
EasyTether i think would be your best option. The free version is full-figured, and paying for the full market version will get you https:// sites. And the drivers for it are available on their website for download.

P.S. it's only $4.99 right now in the Amazon Appstore ;)