Global warming. If you haven't heard about it, you've been living under a rock. If you don't believe it's happening, you're probably living under a rock. And even if you don't believe it's happening, the rest of the world does, and that's going to impact you when resources start getting short.
While small things won't save the earth, they're a step in the right direction. And here's some small steps you can take.
(1) Eat vegetarian one day a week (or one more day a week than you already are.) Raising meat, particularly beef and pork, generally have a horrendous effect on the environment. The good news? It's cheaper to eat vegetarian and better for your health.
(2) Stop drinking bottled water. Tons of petroleum products go into the manufacture of the bottles, and the water is less regulated than tap water. The good news? It's cheaper to use a refillable bottle.
(3) Walk/bike/take public transit one (more) day a week. The good news? It's cheaper and you'll get more exercise.
(4) Seal your home better with caulk and insulation. The good news? It's cheaper than paying the utility and you and your family will be more comfortable.
See? No messy mercury-based CFLs or buying hybrid cars or anything. All stuff that's easy and cheap and good for you. So even if you don't believe global warming is happening, you win.