not open source, but the mormon's offer a nice little program for free: http://www.familysearch.org/eng/paf/

I decided to try the netbook as an ereader about 6 months ago and I like it. The netbook is not as light as an ebook reader, but it is light enough and it is much more versatile. Be sure to get an 8-9 hour battery pack. A touch screen would be nice. A single purpose e-book reader would need to follow an open standard, cost less than $100, have an 8+ hour battery life to interest me.

For my money, the 10" netbooks plus FBreader makes a great book reader. (Add Sage and you have a great offline dictionary too)

The PDF format should be dumped in favor of SVG, the sooner, the better.