Resources
Further reading and sources for things. Definitely useful if you'd like to learn more about the topics laid out here, and how these infos were uncovered in the first place.
Generally, most pages will link to relevant resources or other pages on the Wiki to help make a topic more understandable to those that are unfamiliar with some part of it.
Minecraft Wiki
While the Minecraft Wiki focuses on things for the latest versions, they do provide sources and resources for old, historical things too. At the very least most articles contain a History section, which lets one easily figure out how a system used to look or work until a certain point in history.
Wiki.vg Archive
A big part of this is also the former wiki.vg page, which has since been shut down and merged into the Minecraft Wiki.
Later versions
While the point of this Wiki is to focus on Beta 1.7.3 or thereabouts, we're happy to provide context and info for later versions of the game as well.
The Golden Age Wiki has some useful info, especially regarding how Terrain generation works in Beta 1.8 and onward, as seen here.
Misc
Some remaining stuff can be found on the BetrockServer Wiki, though a lot of it has been transferred over to the Beta Wiki since. It also features an alternative Block ID Listing. The one hosted on grahamedgecombe.com is a great alternative for general usage, especially if you don't care about Metadata, though it may contain blocks that did not exist until a future version. The one currently on the Beta Wiki is generally considered to be better than either though.