52 Weeks to Make the World a Better Place: Week 7 - Use rechargeable batteries where feasible

Batteries are terrible things with respect to disposal and long-term environmental damage. Pretty much all applications requiring batteries can make use of the rechargeable variety. OK, they're expensive and you have to buy a charger, but just do a bit of pricing: how many uses will pay for for the extra cost? 5? 10? 20? (depends on the mAh) The NiMH types (most environmentally-friendly and powerful) claim up to 1000 charges! So they'll save you loads of money long-term as well as reducing environmental damage.

A word of caution, though - always buy the recommended charger with branded batteries!