omg Knerd. I love your thriftshopping idea! Sounds like something my best friend and I should do next time we get together!

The hubs and I go hiking with the kids when we're low on funds and bored out of our minds with the parks around base. So we'll hike a smallish mountain. No funds necessary, just water bottles and some fruit from home.

Geocaching is also a great afternoon activity. I think I got my GPS for $50? Well worth it for the multiple outings it's taken us on.

Fishing is always a fun option, though you'd have to get a permit for that which can be pricey but a one day pass isn't too bad in most locations. (Though, if you don't like fish/fishing it isn't really a worthwhile option)

Building forts out of blankets and couch cushions then watching a movie from inside of said fort is a good pasttime that we use about 4 times a year with the monsters...