Hi Craig,

There are definetely SDK's out there, but there are also Active-X controls and libs that are already tested and do much of the work for you. Besides the links that Borislav posted on this thread. This company came highly recommended and seems to work with a wide variety of biometric devices.

http://www.biometrics.co.za/sol_BioTools.htm

still checking them out, myself. They look good but charge a $50 fee for each reader that you use. While the amount is not the issue the keeping track of which customer has how many readers certainly does not appeal to me..