COPS!

Calibre Web is a web app providing a clean interface for browsing, reading and downloading eBooks using an existing Calibre database.

Lightweight and simple OPDS server for the home use

Ubooquity is a free, lightweight and easy-to-use home server for your comics and ebooks. Use it to access your files from anywhere, with a tablet, an e-reader, a phone or a computer.

Calibre2opds can generate OPDS and HTML catalogs from the metadata of the calibre e-book library manager. These catalogs can then be used both to browse your e-book library online and also to download books on demand.