This is probably not a new thing, however the World Horse Welfare have 4 farms over the country you can visit for free -
Hall Farm, Norfolk
Penny Farm, Blackpool
Glenda Spooner Farm, Somerset
Belwade Farm, Aberdeenshire
Until a couple of weeks ago we didn't know these places existed, however been to Hall Farm twice now and our 2 year old daughter loves it. The cafe wasn't a rip off (eg £1 for a bowl of chips) and it was nice to have a walk round in somewhere non-commercial.
Although it's free, I think most people probably make a donation like we did - however it's nice to think you can pay what you think it's worth and the money is going to something worthwhile.