OK, so you can't afford solar panels, windmills and an electric car, but there are loads of little ways of being environmentally friendly!
Green cleaning Avoid using harmful cleaners and try green alternatives - there are loads in the shops. Try using bicarb of soda and white vinegar to clean toilets, and wet newspaper to clean windows - it really does work! Don't buy wasteful kitchen roll or paper towels - use cloth ones and wash them. Never use deodorizing spray.
Electric goods also come in green versions that consume less energy, and they're dead cheap (and you can buy low-consumption light bulbs etc).
Don't forget to turn electrical appliances off rather than leaving them on stand-by, and when you're brushing your teeth don't leave the tap running!