Carbon offsetting, and flying

So I recently noticed that despite my green light bulbs and biodegradable trash bags, I am still an enemy of the planet. I fly at least 4 or 5 times a year.

The carbon emissions of one flight of 1500-2000 miles is equal to roughly the entire emissions for a four person family home for one complete year. Wow.

Now, situations prevent me from not flying, so I have started offsetting my flights using CarbonFund.org. Not the same as not flying, but it is doing something, right?