The Hitch Hikers Guide to BIM by Alan Wooldrige (codename Cadalot) is very useful guide for anyone who wants to learn about BIM. He uses a live language to make you feel comfortable within a partly alien subject. Though it looks like a concise BIM encyclopaedia with terminologies presented in an alphabetical order, you will find it interesting to read from the beginning to the end. You will surely want keep it as a quick reference guide. As the title implies, it provides you with the essential information for you to survive when you enter into the BIM world.
The Document is being updated, however you can access the current version here.