An acronym whose expansion includes itself. Eg.:

PINE

PINE Is Not Elm

Wine

WINE is not an Emulator?

GNU

GNU’s Not Unix

Cygnus

Cygnus, Your GNU Support

Emacs

Escape Meta Alt Control Shift
or, Emacs Makes All Computers Slow
or, Eight Megabytes And Constantly Swapping (from the days when the common computer had one or two megabytes of RAM)
or, Editing with MACroS

EINE

EINE Is Not EMACS

ZWEI

ZWEI Was EINE Initially

LIAR

Liar Imitates Apply Recursively

LAME

LAME Ain't an MP3 Encoder

Zinf

Zinf Is Not Freeamp

For the ultimate in RecursiveAcronyms see Hurd, a pair of mutually referring RecursiveAcronyms!

Note that XINARA Is Not A Recursive Acronym. Perhaps it should be! (Apparently it's a town on the Tinos Islands, off Greece.) PINARA also isn't, but that's already been suggested on kuro5hin. This was the only [A-Z]INARA I could find in a Google search in this context.