There is another post containing resources for gardeners learning to use plant scientific names. You will find it if you search for "Plant ID". I have added the following new one today:
http://oregonstate.edu/dept/ldplants/2plants.htm Searchable list of common garden plant genera. Click on a genus name to get description and links to many photos of different parts and stages of the plant. It also links to another database, this one providing a simplified plant key for woody landscape plants.