Viewer for quest state and reward information.
gem info viewer (mostly obsolete)
View descriptions of most active skill gems and the advice tooltips for the combinations of skills and supports that the developers thought were worth mentioning. Includes partial listings for many skills not active in the current game (scrapped prototypes, works in progress, and obsolete gems.)
essays
Reading these will drive you mad.
related youtube uploads
A few things from the game I thought deserved videos.