While I have absolutely no need for a modem for communication, I am
interested in using the on-screen "Caller ID" function that is available in
MCE2005. My Sony XL1 did not come equipped with a modem, but it has
several free USB ports.

I haven't purchased a modem in at least ten years, and all the old ones I
have lying around are equipped with COM ports (which my XL1 doesn't have)
and don't support Caller ID.

I only have one free PCI slot, and I want to save that for a second tuner.

Can somebody please recommend a good USB modem for use as Caller ID (which
will be my only use for it)? I am in the US.

TIA.