Dan Kegel's ISDN Page: http://www.alumni.caltech.edu/~dank/isdn/
Ascend Web Page: http://www.ascend.com/
Farallon's Web Page: http://www.farallon.com/
pppd package: ftp://cs.anu.edu.au/pub/software/ppp/
Seyon: ftp://sunsite.unc.edu/pub/Linux/apps/serialcomm/dialout/seyon-2.14c-tar.gz
Spellcaster web page: http://www.spellcast.com/