Yowsa! (trail work) 2:40:00 
My company, Archemix, sponsors a community service day each year where employees help "give back" to the community. Last year, we cut down plants growing along the edge of the Charles river in Cambridge. This year, we rebuilt some trails that lead from Glacken field to the Fresh Pond reservoir.
Lots of wheelbarrowing wood chips, hauling logs, dragging mattocks, etc. Pretty fun day; it was cool to see the product of our efforts.