I think Wikipedia tends to tilt slightly tilted towards the left of center, and slightly towards an EU-centric viewpoint, vaguely along the lines of BBC News's tilt (though theirs is somewhat more pronounced).
How fascinating! I tend to find wikipedia slanted slightly right-wing, with a wide spectrum of people to round it out. It's very interesting that we can get such different opinions of the same group of people.
I honestly hadn't noticed any particular _political_ bias. One of the odd characteristics of Wikipedia is that it is (a) huge, and (b) doesn't lend itself to getting any kind of synoptic overview--so one's view of Wikipedia is strongly shaped by the articles you care to read and/or edit. So how you see Wikipedia becomes a kind of projective test.
Drove up a newcomer in a covered wagon: "What kind of folks live around here?" "Well, stranger, what kind of folks was there in the country you come from?" "Well, they was mostly a lowdown, lying, thieving gossiping, backbiting kind lot of people." "Well, I guess, stranger, that's about the kind of folks you'll find around here." And the dusty gray stranger had just about blended into the dusty gray cottonwoods in a clump on the horizon when another newcomer drove up: "What kind of folks live around here?" "Well, stranger, what kind of folks was there in the country you come from?" "Well, they was mostly a decent, hardworking, lawabiding, friendly lot of people." "Well, I guess, stranger, that's about the kind of folks you'll find around here."
--Carl Sandburg, _The People, Yes_
(I'll save "The Blind Men and the Elephant" for another day).
-- Daniel P. B. Smith, dpbsmith@verizon.net