I just run across a rather strange one that some might enjoy if they into walks in the country.
I hadn't heard of it before, but it's
Geocaching.
As far as I understand it, the basic deal is that you look for Geocaches in your area, visit it and sign the log book in the Tupperware box.
But there's others, some are puzzles that lead to other Geocaches, some have a task involved..
Anyhoo, all the various types are here..
http://www.geocaching.com/about/cache_types.aspxI dunno, maybe it's the type of thing that might give you something to do with the kids of a Sunday.
(I found out that the Barons Haugh estate in Motherwell was set up in about 870 and I was only on the site for five minutes..

)