The bunny, or rabbit, is one of the most fertile and prolific of creatures and served as a pre-Christian symbol of new life in Springtime.
It appears that the Germans may have been the ones to introduce the bunny as an Easter symbol. There is evidence in writings in the 1500s to that effect. It wasn't until the 1800s that the first edible bunnies were made, again by the Germans. These were not chocolate, but pastries.
Apparently, the Germans brought the concept of the Easter bunny to America in 1700s when they traveled here with the Pensylvania Dutch.
Please see http://www.easterbunnys.net/easterbunnyhistory.htm for more information.
Interestingly, it seems that the goddess Eastre, or Eostre, had a consort. That consort was a Hare, similar to a rabbit, but even larger. The egg, like the hare, was also a symbol of fertility. It was believed that the goddess gave the hare the power to lay eggs, but only once each year.
When the Germans came to America, the concept of the Easter Bunny,or Oschter Haws, came with them. The children would make nests out of their bonnets and caps, then hide them, hoping the Oschter Haws would leave them colored eggs.
http://www.associatedcontent.com/article/19144/the_origin_and_history_of_the_easter.html?cat=7 For more detailed information.