Start a compost heap. Will cut down on the amount of rubbish you throw away and help the garden. You also have the added bonus of knowing what went into making the compost, which is something you won't know when you purchase it from the garden centre
Look into growing your own food. The whole family can be involved in a vegetable patch, children will learn that carrots come from the ground not the shelf and you can all get fit and healthy
Plant fruit trees and shrubs such as apples, pears, raspberries, strawberries, etc
Start a herb garden. If you don't have a garden, use a window box or pots. Fresh herbs always taste better. Many plain and bland meals can be given new life by the addition of herbs
Use old net curtains or bubble wrap to keep tender plants warm
When sowing grass seed, surround the newly planted area with twigs and string cotton across the patch from twig to twig to discourage birds
Fit water butts to your drainpipes and use to water the garden and clean the car
Consider buying a "patio heater" which can be used to burn excess packaging, etc, and reduce the household rubbish that won't fit into the bin anymore