Citizen Science projects you can do in your backyard
http://www.greatsunflower.org/ Observe bees - They'll send you sunflower seeds to plant, if you'll record information about the bees seen on the flowers.
http://www.spiderwebwatch.org/ Spider WebWatch - The nine species they are tracking are relatively easy to identify and can be quite common. They were specifically chosen because they are native to North America.
http://www.nwf.org/frogwatchUSA/ Frog Watch USA - Learn identification of frogs and toads and record your counts. It is up to you how often your site is monitored. Your data would be most useful if you could monitor at least twice a week throughout the breeding season.
http://www.windows.ucar.edu/citizen_science/budburst/index.php Project Bud Burst - Are the plants changing their cycles due to environment or climate changes? They list and id the plants they are interested in tracking. You record when you see the First Leaf, First Flower, First Fruit Ripe.
http://www.mos.org/fireflywatch/ Firefly Watch - Record activity during the summer season. The scientists hope to learn more about the environmental factors effecting the fireflies habitat.
http://www.mlmp.org Monarch Larva Monitoring Project - report any sighting of Monarch butterfly egg or larva