Apple has a discussion forum going on this very card, but I couldn't make heads or tails of which was actually the right solution. So, I present to you here, screenshots and a walkthrough of the setup.
1) Purchase a Verizon Pantech UM175, one of the latest USB wireless cards from Verizon. Should be able to get it for $0 with a 2 year contract.
2) Plug it in. Mac OSX 10.5 Leopard will detect it as a modem
3) Change the settings per the screenshots below
3.a) Vendor: Sierra, Model: CDMA, Dial Mode: Ignore dial tone when dialing
3.b) Telephone Number: #777, Account Name: YOURNUMBER@vzw3g.com, Password: VZW
