General Encyclopedias are great for browsing and brainstorming on your topic. Read for background on your topic, watch for keywords and phrases that define your topic, note the sub-categories where you might focus your paper, and finally record the names of important people in the field, like the author of the article, and the authors found in the bibliographies or further study sections at the end of the articles.
Gale Virtual Reference Library is a database of over 650 digitized specialized encyclopedias. It is possible to search all of the encyclopedias at the same time or within a subject area, or you may select a particular title and search only within that publication.
Credo provides full-text online versions of hundreds of top quality reference books in all major subjects from art to medicine, psychology to history, and technology to literature. Keyword search or browze by subject. Also contains images and a maping feature to find similar topics.
Anyone can update Wikipedia articles so proceed with caution. While Wikipedia might be considered a good information source you may not want to rely on it as your only source.