caller id.
Author : Jamie Zawinski
Website : *www.jwz.org/cid/
From one of the original Netscape developers - should work OK.
mgetty
Author : Gert Doering
Website : *www.leo.org/~doering/mgetty/ will have the latest version but the website's not actively maintained
FAQ :
ftp://ftp.leo.org/pub/comp/usenet/news.answers/fax-faq/mgetty+sendfax+vgetty.gz
This comms package, found in many distributions, apparently handles Caller ID well, and can respond differently to particular numbers.
NumPres
Author : Hermann Björk
Website : was at *www.flashback.net/~hermann/numpres.html
This program doesn't have a GUI yet, but might be worth checking out. It requires you to build some hardware based on the Mitel MT8870 chip for decoding DTMF-style Caller ID.
Voxilla
Website : *voxilla.org/top/apps.html
Voxilla is a site that is trying to coordinate the development of a complete suite of telephone tools for Linux. It's fairly early days at the moment, but it's worth keeping an eye on.
--------- enjoy