I’ve been a subscriber to Wizards of the Coast “Dungeons and Dragons Insider” from the beginning mainly for the Dragon Magazine, and Dungeon Magazine content. In fact, for a while I considered the D&D Compendium kind of useless. After all, I already own the book, right? Maybe, but not quite.
Basically the D&D Compendium is a database of all the D&D rules published by WOTC. This includes major releases like Monster Manual 2, but also Dungeon and Dragon magazines, and RPGA adventures.
As a DM you can use it to find creatures based on name, then sort by type, role, level, or XP value. In addition, you could search for a specific power and then find creatures with that power. Just as an example, there appear to be about 41 different kobolds in 4E already, though I’m always looking for more.
As a player you can search for Feats, Powers, Paragon Paths or Epic Destinies. For example, I did a search for speed and found a feat called ‘Shared Speed’ which allows a familiar and his owner to share a speed bonus.
And when it comes to owning the books, you don’t have to, as long as you have your subscription, all that information is yours. Even though I have yet to purchase the 4th Edition version of Manual of the Planes I can still see and print the stats for the Barbed Devil from that book.
So, if like me, you subscribed to D&D Insider for the magazine content, or perhaps for the Character Creator, make sure you take the time to try out this outstanding resource.