Today we are preparing to accept the ubiquitous library age. This article will serve to define the concepts of the hybrid library, the gateway library and the ubiquitous library which hold the advanced concepts of the digital library. It will review the main projects about them in order to portray what the future libraries will be like and how they can be developed. In particular, the eLib program of the hybrid library, the gateway projects by Harvard University and Penn State University, and the ubiquitous library projects in Carnegie Melon University and Maryland University will be surveyed, through which the characteristics of the information services being operated by the ubiquitous libraries will be scanned.