Planting trees
Pay $200 to plant a tree? I planted one for 'free' in the army camp two months ago. I think it is thriving very well. (This warrants a visit to camp again, and catch up with everyone)
What happened was that I came across a young banyan tree (Ficus sp.) growing in a plastic pot. Clearly, some birds had deposited its seeds in the pot, probably via its faeces. The roots were constrained by the pot, and I'd cut open the pot and planted it in the ground. It established itself quite quickly, and within a few weeks, new shoots were forming. Before that, it had been shedding leaves...
Trees aren't just wonderful to look at, but also provide valuable habitat and food for wildlife. Imagine the amount of carbon dioxide that will be locked up in the tree during its lifetime's growth...