While cruising Smartphone Thoughts (a good resource for other WinMo5 users in the audience) and their forums, I found this post at Mobility Today by David Ciccione that describes how to use a BlackBerry 3G Driver (of all things) to tether a BlackJack to a Mac for getting online. It isn't a simple process, but I just went through the paces and can confirm - it works.
Now before you run off and start tethering your BlackJack to your Mac all over the place, I want to add a few things to Mr. Ciccione's awesome work so everyone in our diverse audience knows what they're getting into. First off: if you don't have the proper data plan with Cingular, I have no idea if or how much they'll charge you per KB or MB for connecting, even if you're just testing this out. Try this at your own risk - we can't be responsible if you connect and start downloading movies from the iTunes Store, only to get a $300 bill for data next month. Call Cingular, like I did, before you goof around with this to make sure you have the right data plan. For what it's worth, I have the $20/month Smartphone unlimited data plan, which gets to fly under the radar of their ~$50 PDA data plan since it's a 'Smartphone' instead of a full-blown Pocket PC phone or data card for a notebook.
Continue reading after the jump for some add-on tips and gotchas to make this a smooth and worthwhile process.
Upon connecting the phone, you should see a new "Samsung CDMA Technologies" item under your available network ports in the Network System Preference pane (before you ask: I have no idea why the title is 'CDMA' when this is a GSM phone and service). After your first successful connection online, it should also get listed as an always-available port, right next to AirPort (like my screenshot here) and any other ports you have used in the past.
I would also like to add a 'step 11' to David's instructions, as the end of his post gets a little unclear, at least to me. In the Modem tab of the Network pane's configuration, be sure to check 'Show modem status in menu bar' (if you haven't already), otherwise you might have to use something like the Internet Connection app (in your Applications folder) to toggle your connection and get online.
If all goes well though, you can select 'Connect' from the menubar item to get online. For me, connecting was pretty quick, though speeds aren't exactly like the ~ 6Mbps Comcast high-speed I enjoy at home. That might also be due to my residence just outside of Denver, CO, where we haven't risen to the ranks of HSPDA quiet yet. Fortunately though, I hear San Francisco is all but drowning in the high-speed wireless network, which means I can use this to get online during Mr. Jobs' keynote at Macworld '07.
So that, in a not-so-nutshell, should do it for getting your Mac online with a Cingular BlackJack. I have no idea if this will work with other phones, but if you have questions about this process or the BlackJack itself (which I'm really happy with, considering), feel free to fire away in the comments.