so far VoiceTronix look the best bet, although the CTI cards look a little steep at 500 dollars. They have drivers for linux, etc and provide nice OSS libraries with interfaces for perl. The perl API is on CPAN, contributed by one of their developers.
Another handy website I found was TuxMobil, with its list of linux based telephony and telecoms-related servers and projects. Handy.
Any other perl mongers familiar with CTI want to chip in with some warnings, or advice?