Is there any central collection where I can find OllyDbg plugins? I often see people say things like "simply use this plugin or that plugin" on this board, but I cannot find these plugins anywhere.

dELTA: you can find them at OllyDbg Users Stuph ("http://www.rohanpall.com/ollydbg/files").
i will put a link sometimes on the first page ... sometimes

TBD >> a links section will be good