Edit text with vi(1) by Roman Zolotarev
vi is not vim by Hugo Daniel (thanx @gaborkiss)
vi help by Jeff W
vi reference by Maarten Litmaath and James Hu
vi editor cheat sheet by ericg
vi wikii by Blake McBride and Arahant, LLC
Graphical vi cheat sheet by ViEmu
vi Quick Rererence via mpaoli.net (PDF)
The vi archive and FAQ (a mirror) by Ove Ruben R Olsen
Annotated .nexrc by Sehnsucht