Carbon Footprints

Recently there has been an explosion of sites on the web devoted to helping individuals calculate their Carbon Footprint and then giving them ways to reduce it. I have several issues with all of these sites and I am yet to find one that I find genuinely useful. The main issues I have is that they all seem to calculate your footprint differently. On some sites I have an exemplary footprint on others I have doomed the earth to fall apart next week. Is there a standard way of calculating a footprint and if so why don't these sites all use it? Secondly none of the sites that I have visited actually put into context what a tonne of CO2 is and what effect a tonne has on my daily life. I'd just like a way of putting my footprint into context. Finally, I need to feel that as an average person I can make a difference. I recycle, all my light bulbs have been changed to energy efficient versions and I don't put my telly on standby - oh and I also have a water butt. The strange thing about reducing your carbon footprint is that after you've done the basics things suddenly become very expensive. Have you ever got a quote for anything solar? What about burying a brown water tank in the garden. It's very difficult for the average person to justify the cost and with the government reducing grants and the competition for them. These alternatives are out of reach for most people.