Dragon Magazine
Dragon Magazine was, alongside Dungeon Magazine, one of the two official monthly magazines supporting D&D. It was in print from 1976 - 2007 published by paizo, then bought back by WOTC and published as a PDF support of 4e. It was quietly put out of its misery in 2013 when 5th edition became a thing, and probably won't be back any time soon. Who the fuck buys dead trees in 2016?
We can all blame Hasbro, of course. Soul-less, emotion-less automatons that they are. Like passively malicious modrons.
Over its venerable 31-year run, Dragon Magazine was responsible for providing a huge amount of content. Although some aspects proved only short-lived (Giants In The Earth, for example, an article that converted real-world or fantasy novel/game characters to D&D statblocks, didn't make it to the 3e switchover), it provided a huge array of races, magic items, spells, feats, classes, and other crunchy goodness of... admittedly somewhat variable quality.
A bunch of 3.5 content was collected into Dragon Magazine Compendium Volume 1 (no volume 2 was ever published). The content is considered mostly balanced, if not on the weak and uninspired side (most of the base classes printed are effectively variants of existing classes). The bloodline feats (Give a sorcerer bonus spells in exchange for prohibitions on casting opposing spells. Would become a standard part of the Sorcerer class in latter editions and Pathfinder.) and Force Missile Mage (a casting prestige class that specializes in Magic Missile) are notable inclusions. Unlike Dragon itself, the compendium is generally allowed in games/optimization contests that allow all first party books.
In fact, the content of pre-4e Dragon content is so huge that there's actually a website that tries to serve as an encylopediac reference for the whole mess, which you can find here: http://www.aeolia.net/dragondex/