Whether you are just getting started in the E&P industry or you are looking for help with an unfamiliar term or concept, try the SPE (my personal favorite), AAPG, and SEG wiki pages. These wikis are verbose and filled with good citations; providing clear, more accurate information than the traditional wiki – Wikipedia.
What is their source material?
Many of these wikis have core material built upon some existing publication: the SPE Petrowiki is built on the Petroleum Engineering Handbook; the SEG Dictionary is built on the Encyclopedic Dictionary of Applied Geophysics; etc.
Who edits these wikis?
These pages are maintained largely by student members with some degree of scrutinization by other members. So, they each have varying degrees of what can be considered APPROVED material; so accuracy cannot be guaranteed 100% (but still far better than a generic google search).
Where can I find them?