Jersey Yards has a great site that is very easy to use for beginners who want to improve habitats and conserve water.
Bringing nature home also has a more insect oriented site with great pictures of the insects you can attract if you plant certain trees. The science of supporting foodwebs with native plants is explained well here. This site is maintained by the research program of Dr. Doug Tallamy of University of Delaware. There is also a ‘what should I plant’ function. This is my favorite of the sites.
New Jersey Native Plant Society
The Native Plant Society maintains a comprehensive page with plant lists and instructions on how to plant a rain garden. This site is recommended for more advanced gardeners and people with interests in more comprehensive issues than (sub)urban gardening. http://www.npsnj.org/pages/nativeplants_Plant_Lists.html