The Diablo 2 Wiki
The Diablo 2 Wiki archive is available for anyone looking for information on Diablo 2. All information here is pre-D2R but contains a lot of useful information that is still relevant. Updated sections for new D2R features can be found on the PureDiablo Diablo 2 section

Diablo 3

From Diablo 2 Wiki

On June 28, 2008, Blizzard officially announced Diablo III, in Paris, at their World Wide Invitational exhibition. This wiki page formerly held an extensive article, documenting the numerous rumors and bits of information leaked about Diablo III's development, before the official announcement. That page can now be seen here, in our Diablo III wiki, along with full coverage of everything else about Blizzard's upcoming title.

Diablo III title image.