Maintaining large collections of Ebooks can become a nightmare, if not maintained properly finding the desired books is also a difficult job. Calibre is a one word solution to this problem. calibre is free and open source e-book software that organizes and manages e-books, supporting a variety of formats. It also supports e-book syncing with a variety of popular e-book readers and will convert e-books between differing formats.
Calibre helps you catalog your e-book collection. First, it surveys all the e-books and other relevant files residing either on your hard drive or your e-reader, and then inserts them into Calibre’s main directory. Once that information is in the directory, you can use it to organise, categorize, annotate, search, rate and save to disk. You can customize or delete any of the data fields Calibre fills in, or add your own.
Its main features are :
- Library Management
- In addition, it supports extra searchable metadata:
- E-book conversion
- Syncing to e-book reader devices
- Downloading news from the web and converting it into e-book form
Calibre can automatically fetch news from websites or RSS feeds, format the news into a ebook and upload to a connected device.
- Comprehensive e-book viewer
- Content server for online access to your book collection
Calibre serves the purpose it was made for efficiently so you no longer have to worry about searching your whole file system to find an ebook. I have found it to be one of the most usefull software in the opensource world. Especially the feature to share your books online is an added advantage and setting up the calibre server is an easy task.

Calibre is availble for Windows ,Mac and Linux. A portable version of calibre is also available so that you can carry around your library in a pendrive, Installing calibre is a straight forward affair and in ubuntu it is available in the software center. I hope this article serves as an introduction to calibre for those who have not yet heard about it.
Check http://www.calibre-ebook.com for more details.