You'll be very surprised to learn that there aren't very many of these. Here is what I found.

Machine and Microprocessor Pages

Planet Sinclair's MK14 Page. Probably the next best information site on the MK14. Contains the MK14's history and details of other Sinclair products.

http://www.nvg.unit.no/sinclair/planet/mk14fram.htm

Great Microprocessors of the Past and Present. some info on SC/MP Microprocessor

http://www.cs.uregina.ca/~bayko/cpu.html

About the SC/MP Microprocessor

http://www.realtime-info.be/encyc/techno/terms/83/80.htm

A page about the SC/MP Introkit

http://swift.eng.ox.ac.uk/rjm/museum/NationalSemiconductorSCMP.html

Personal History Pages

Some home pages of people who learnt to program on an MK14.

Ray Aucote

http://ws4.u-net.net/~aucote/comp.htm

P K Shiu

http://www.imperial-consulting.com/pk_comp.htm