1902 Encyclopedia - http://www.1902encyclopedia.com/
Features articles from 9th and 10th editions of encyclopaedia britannica.
Mashpedia - http://www.mashpedia.com/
Featuring videos, text, images and audio for every topic.
Plant Encyclopedia - http://www.plant-encyclopedia.net/
Features a searchable database of garden and house plant information organized alphabetically. Also includes images and cultivation tips.
Scholarpedia - http://www.scholarpedia.org
The peer-reviewed open-access encyclopedia, where knowledge is curated by communities of experts.
The Encyclopedia of House Plants - http://www.gflora.com/
Provides listings of house plants with information and pictures. Includes online store, plant identificator, news, events, and newsletter.