There is probably less targeted to kids online that is nonfiction. Many kids (frequently boys) are much more interesting in nonfiction than in fiction, which seems 'babyish' to them. Nonfiction reading is a good way to draw boys in, and it's also a good way to introduce girls to facts rather than stories. Both boys and girls are often very interested in animals.
Bartleby's, as mentioned on previous pages has searchable content, both fiction and nonfiction. The nonfiction link appears here, but it's easy to get from one to the other using the 'fiction' or 'nonfiction' tabs on the page. These are expired copyright materials, and mostly aimed at adult readers. They are better probably for searching for words in context than for finding materials for the child to read. | |
Cobblestone, focused on American History for kids, has some very interesting (but nonsearchable) free articles. | |
For nonfiction, you should also see the page on searching the Web. |