I'd get a Lectron I56PSP/F40 PCI modem from Ascent (http://www.ascent.co.nz/mn-product-spec.asp?pid=120287). $20.93, and it works well in linux.
Get the ltmodem drivers from http://www.physcip.uni-stuttgart.de/heby/ltmodem/. If you're running FC2 on a P2 or Celeron or later, you'll *probably* be ok to get the binary release drivers - make sure you get the right one for the kernel you are running however!
Just following this up - there are (or were, when I looked a month or two back), two sets of binary drivers - one for i386, one for i686. Except, the ones targetted for i386, were actually still compiled for i686. This means they will not work at all on an i586 system, such as a pentium, or a k6 or k6-2 processor. If you've got a Celeron or Pentium 2 or later, or an AMD Athlon or Duron, you'll be fine. Daniel