Mendeley is a free bibliography manager. Annoyingly, it is not open-source. But it is superior to endnote.

It makes researching easier. PDF’s can be sync’d with an online account (500MB for free). Article information is read from the PDF and checked using google scholar. A PDF viewer is included and the your collection’s meta-data can be searched.

An online account must be created first. Then installation is simple for both Windows (.exe) and Ubuntu Linux (apt).

Open-source alternatives are available (1,2,3). Though these alternatives lack the above functionality.