freeads/adtrader..your local tack shops sometimes have boards with adverts..local riding schools and yards they tend to know everything about everything..advertise yourself in the wanted sections of papers and where ever you see cards in the shop windows etc.any horse shows around go to them and ask about but also you could leave your details with the rspca as alot of times they need urgent places to put rescued horses and if your chosen most of the time you can actually just keep them i was given two once by them and i was allowed to bring them on and rehome them.depends what your after really...good luck