Source - stateoftheair.orgWhile you can't do too much about the outdoors short of wearing some sort of mask, you can try to control air polution indoors with an air filter.
I'm a fan of alternative transportation (vs regular gasoline powered cars). Personal transportation in particular is one that I feel more people can improve upon in their lives. Does it really make sense to drive a 2 ton vehicle out for a local trip to the grocery store or rent movies? What a waste!
Sadly, at least in most of California, I see few people using alternative transportation for such short local trips. I've seen one segway, a few bicycles used by some staff, a motorcycle every now and then, and a handful of people who walk from across the street here in So. Cal.
Go-ped goes a long way into making personal transportation fun and practical. They recently released a line of bulletproof kick scooters that I think everyone should consider in an urban / city / metropolitan environment.
I recycle. Cans, paper, bottles, computers, electronics, water, etc.
I use solar energy (directly from sunlight) to charge my every day batteries that power my portable electronics, cell phone, laptop, and lights in my computer room.
I turn off lights when the room isn't being occupied.
I switched to high efficiency fluorescent tubes and LED lights.
My servers are on a timed schedule and power down when unused for a long period of time.
I vote for energy star rated efficiency products when I make my purchases.
My web-server is completely powered by solar and wind energy.
I use rechargeable batteries instead of disposables for almost everything except a watch or two, and those last for years before they need to be replaced.
I take short showers.
I eat home grown vegetables and fruits.
I unplug AC adapters when the electronics won't be used for a while.
I put on an extra layer when it gets cold at home vs using a heater.
I try to pass out virtual contact/business cards vs paper cards.
I don't ask for a receipt at starbucks.
I mulch my grass clippings to use as fertilizer.
I pay with e-bills and use virtual statements.
I use re-usable water bottles made of aluminum, which itself is completely recyclable.