webcam ...

IPL98 - Portable Image Library
the IPL98 portable image library has a camera add-on library
http://www.mip.sdu.dk/ipl98/

Microsoft Vision SDK
After some developers forum recomendation "Microsoft Vision SDK" would be the best to develop webcam capturing applications. Microsoft unfortunately sold the vision sdk to a german company, it is no longer available for download on their reseach lab homepage.