APL Wiki
Vendors
Different vendors provide different implementations of APL. (Your mileage will definitely vary.)
[http://www-306.ibm.com/software/awdtools/apl/ IBM] sells APL2
[http://www.apl2000.com/ APL2000] sells APL+Win
[http://www.microapl.co.uk/apl/ MicroAPL] sells APLX
[http://www.dyalog.com Dyalog] sells Dyalog APL
[http://www.soliton.com/services_sharp.html Soliton] sells SHARP APL (SAX on Unix)
[http://www.jsoftware.com Jsoftware] sells J, an APL completely redesigned about 1990.
[http://www.kx.com Kx Systems] sells K and Q, blends of APL and Lisp.
See also WhichApl and AplsAndRelatedLanguages.