With the announcement that Encyclopedia Britannica is ending it's print version and going digital, on comes the mobile apps. Mobile apps are being created for edu use focused on popular subject area.
I came across Brittanica Kids: Rainforests which is free as of now. Other topic areas include: knights, snakes, us presidents, volcanoes, ancient rome, etc.... Encyclopedia Britannica's Mobile Site takes you to a complete list, with more coming soon. All priced from free (rainforest) to $4.99.
Britannica Kids: Rainforest **FREE**
I put this on my ipad and had fun looking at the article, with great vocabulary (linkable to the definition), games, video and picture resources, interactive maps, etc. There are also a rainforest animal resources page which lists over 20 animals with an article about each.
Of course....Encyclopedia Britannica has a free app listed as well... but requires a $1.99 subscription per month for full privledges. Always free is the this day in history or the most popular articles. Within the articles it links to images that are scrollable and has a great web of related articles. (See picture)