Calibre
From Just Solve the File Format Problem
Calibre is an open-source ebook library management tool with extensive features for converting ebooks between virtually all known ebook formats. Extensible design with many plugins available. Although a standard Calibre install does not include features for converting files from formats that include digital rights management (DRM), some third-party plugins exist that allow conversion from these formats. Software is cross-platform and written in Python.
