I took up geocaching about 4 years ago as a way to get fit after a car accident after someone on mumsnet suggested it. Ds used to come too, but now he's a teenager everything is boring, especially anything mum wants to do! I still manage to drag him out with me occassionally though.
It's a really cheap hobby, has taken us to some interesting places and I've learnt lots about the area I live in that I never knew - Hidden nature reserves, history, architecture, stunning scenery and footpaths that I'd never have explored otherwise, to name just a few.
I am lucky that there are also lots of geo events in my area, so I've met lots of other who share this hobby and we've had some fun adventures. Now that ds doesn't want to geocache with me I sometimes go alone and sometimes meet up with others to go caching in groups. It's also a good way of exploring a new area if you're away on holiday or visiting relatives or just out and about somewhere for whatever reason.
I have made some new friends through it. Geocaching appeals to people of all ages and from many walks of life. There are lots of others who come to events both with and without their partners. There are several other ladies at the events I go too who come alone, some are lone parents too.
If it's too wet/dark to go out in the winter I can sit and plan where I'd like to go when the weather is better, or I can try and solve some puzzles caches too. I can highly recommend it as a cheap way to get yourself out of the house. All you need to get started is a smartphone or a GPS device.