Thanks to all for the responses.  Here is a summary of the answers.
Datom Engineering (NA contest software) markets the Contest Voice Blaster 
software.  Info about it can be found at http://www.contesting.com/datom.
W9CF has some free software that uses the SoundBlaster as a DVK, but it 
only works with TRlog.  More info at http://fermi.la.asu.edu/w9cf/.
Several people also mentioned the WriteLog contest logging program which I 
already knew about.  In addition to supporting DVK on a SoundBlaster, it 
also uses the sound card for RTTY, PSK, and CW.  More info at 
http://www.contesting.com/writelog.
    73 de Doug, N6RT
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   Doug Brandon       http://members.home.com/dab         dab@home.com
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