This is related to my review of the Kobo eReader.
The Calibre ebook management software is free and open source. To my surprise it supports Windows, Mac and Linux (I used it on Linux and it works perfectly)!
Calibre is basically software which allows you to manage your ebooks, convert them from one format to another and interact with your eReader (copy/delete ebooks from device, etc). The converter is quite advanced and has a wide array of options for people interested in fine tuning their conversion. The nice thing is that it supports most of the eReader devices out there and it has built-in templates so you can convert your books into a format suitable for your particular device. Its quite easy to use while still catering to power users.
If you buy an eReader, I would say this software is a must have. Especially with the increasing number of books and documents now available in digital format, you can be sure to be able to read everything on your device. Do check it out!