Sane (Scanner Access Now Easy) is a project that aims to implement a universal system to access scanners and digital cameras. Much like Twain in scope, it is a better concept separating the scanner-specific backend from the frontend, and supports a multitude of scanners, either locally attached or accessible via the network. The project web site lists supported scanner models and holds the source code for download. Sane runs on a multitude of platforms, including OS/2.
I use this program a lot now because it's easier to work with than Sane and gives consistently good results. It's an excellent replacement for the Nikonscan software.