I consider Wikipedia to be one of the single greatest resources of our current time. Though many people may disagree with me, as a site designed to offer a general overview of various topics I feel that it completely fulfills its mandate. Many times Wikipedia has promoted my increased interest in many topics, many of which I did not previously know exsisted- an example could be thought experiments or the Hawthorne effect.
Many schools, mine included, discourage the use of Wikipedia, but I find it a noble internet institution. It is always easy to introduce information I discovered on Wikipedia into a discussion at school, which I find gives me a general appearance of intelligence which was brought upon by a quick 5 minute search. I will quote a fellow user, billscottbob, whom I feel sums up how to use Wikipedia perfectly:
Wikipedia is an amazing site, especially for off-the-wall and rapidly changing topics but must be used with caution, as you would with any other source.
I will conclude by saying that I feel that Wikipedia is the most complete and most easily accessible online encyclopedia to be found.