Currently supported cellular modems?

[Ralith]

I recently upgraded my laptop from an old acer model running linux w/
a sierra AirCard 860 pcmcia cellular modem (which has semi-official
linux support) to a nice shiny new Asus c90s built from barebones
running, of course, FreeBSD (7.0). This is a wonderful configuration,
except instead of a PCMCIA card slot, it's got an express card slot,
meaning I need to get a new cellular modem. What USB or (preferably)
express card cellular modems are supported? I'm looking for something
with HSDPA support in particular, and an external antenna connector is
always a plus. Also, is there a way to check if my (empty) express
card slot is properly detected and supported by FreeBSD?