Wikipedia is an encyclopedia written collaboratively. Though useful for basic background information, "The upside of Wikipedia is that it is an encyclopedia that ANYONE can edit. But the downside is that it is an encyclopedia that ANYONE can edit."
If you need information about philosophical subjects, persons, places, etc., then GVRL and the Stanford Encyclopedia of Philosophy are good places to start.
Stanford Encyclopedia of Philosophy is a dynamic reference work written, refereed, and maintained by over 950 professional philosophers.
Gale Virtual Reference Library (GVRL) is a collection of encyclopedias, almanacs, and specialized reference sources;these trusted, authoritative reference works are available 24/7.
PhilPapers is a comprehensive index and bibliography of philosophy maintained by the community of philosophers.