There are a number of ways to recycle a satellite dish, from proper disposal where it's recycled by the trash/recycling company to creative uses that give the dish a new life.
If the dish was installed by a satellite TV company, there is always the option of returning it to the company, so they can recycle it properly.
Check with your local trash/recycling company about rules and regulations. Some companies won't take such devices, but if they handle recycling there is a good chance they will.
Donate your dish to to the not-for-profit Texas Sunflower Project (see Resources).
Donate it to a local amateur radio club. Many ham radio operators have uses for unwanted dishes (see Resources).
If you have an older, 10-foot dish, it can be used as the roof of a gazebo.
Use it as a shallow pond in your yard. A number of gardening magazines have written articles on how to do this. It can also be turned into a shallow bird bath.
Drill holes in the satellite dish and mount it upside down on a pole. Use S-hooks to hang plants on it.
Unused satellite dishes can also be transformed into garden sundials and fountains with a little creativity.