One resource to identify houseplants is the Better Homes and Gardens Plant Encyclopedia. This online encyclopedia is a searchable database for identifying plants based on a variety of characteristics.
To use the encyclopedia, go to the homepage, and select "Houseplant" as your plant type. Select characteristics related to your houseplant, like the type of sunlight it requires, what the foliage and flowers (if any) look like, the plant's height, and other features, and click "search plants." The encyclopedia generates a list of plants that fit the characteristics you provided, including pictures, descriptions and care instructions. Click the name or photo of the plant for more detailed information.