CA-Clipper

Official home page.
http://www.grafxsoft.com/clipper.htm

FlagShip

A database development and porting system for moving xBase based languages to UNIX.
http://fship.com/

Harbour project

A public project for an open source Clipper language compatible compiler. It will become a 100% Clipper compatible compiler for multiple platforms and includes all source code
http://www.harbour-project.org/

Alaska Xbase++

A 32Bit compiler for the Clipper/Xbase language on the Windows platform.
http://www.alaska-software.com/

Clip

Object oriented, CA-Clipper and Xbase compatible compiler.
http://www.english.itk.ru/clipper/

Cl2C

CA-Clipper to C compiler.
http://www.geocities.com/cl2cru/

nanoBase

A GPL'ed xBase-compatible system for DOS.
http://www.simtel.net/pub/pd/42999.html