This site covers bias at the Wikipedia online encyclopedia, specifically that related to U.S. political matters.
Our primary concern is with material information that's missing from particular entries. That's the most pernicious form of bias, and one to which WP's entries are particularly susceptible. The statements made in a WP entry can be double-checked, but those who aren't familiar with a subject won't realize what's missing from the entry.
You can register for an account and submit posts, but to be featured here, something must be:
1. In the English version (en.wikipedia.org)...
2. concern U.S. politics...
3. be fully documented...
4. be something that renders the WP entry misleading...
5. and, be a long-term or continuing issue.
Unfortunately, WP appears very high in search engine results for very many terms, making it appear that WP is an authority on almost every conceivable subject. If an entry contains misleading information, hundreds or thousands of people could be misled before the entry is corrected, if it ever is.
This site strongly recommends against linking to Wikipedia.
Note also that WP has a very strong anti-blog, anti-citizen journalism, pro-mainstream media bias. Their definition of what is a reliable source is truly atavistic, harkening back to the "bad old days" when the three television networks and newspapers were the only source for news.
From their "Reliable sources" guidelines :
Editorial oversight - A publication with a declared editorial policy will have greater reliability than one without, since the content is subject to verification. Self published sources such as personal web pages, personally published print runs and blogs have not been subject to any form of independent fact-checking and so have lower levels of reliability than published news media (e.g. The Economist)...
Of course, if they had, instead of "The Economist", offered as examples "the AP, Reuters, AFP, the New York Times, the Washington Post, or the Los Angeles Times" we could have all had a laugh at their expense. Those mainstream sources - the ones that WP considers above reproach - frequently publish biased, misleading articles and outright lies. The same, of course, is true of self-published sources. And, almost all mainstream sources are careful to avoid libelous statements. However, the idea that all statements made in mainstream articles are true or unbiased or have been fact-checked is proved false by endless examples.
They make a minor exception :
...Anyone can create a website or pay to have a book published and then claim to be an expert in a certain field. For that reason, self-published books, personal websites, anonymous websites, and blogs are largely not acceptable as sources... When a well-known, professional researcher writing within his or her field of expertise, or a well-known professional journalist, has produced self-published material, these may be acceptable as sources, so long as his or her work has been previously published by credible, third-party publications. Editors should exercise caution for two reasons: first, if the information on the professional researcher's blog (or self-published equivalent) is really worth reporting, someone else will have done so; second, the information has been self-published, which means it has not been subject to any independent form of fact-checking.
Even this exception requires someone to be a member of the mainstream media "club". And, of course, what is worth reporting and what the mainstream media considers worth reporting are frequently two very different things . And, while there are huge problems with blogs, many do allow comments and many high-traffic blogs are frequently fact-checked by both visitors and other sites.
WP even goes further :
Personal websites, blogs, and other self-published or vanity publications should not be used as secondary sources. That is, they should not be used as sources of information about a person or topic other than the owner of the website, or author of the book. The reason personal websites are not used as secondary sources - and as primary sources only with great caution and not as a sole source if the subject is controversial - is that they are usually created by unknown individuals who have no one checking their work. They may be uninformed, misled, pushing an agenda, sloppy, relying on rumor and suspicion, or even insane; or they may be intelligent, careful people sharing their knowledge with the world. Only with independent verification by other sources not holding the same POV is it possible to determine the difference.
Aside (perhaps) from "insane", most of the preceding criticisms have at times applied to the mainstream media that WP finds acceptable. Of particular note, the idea that a newspaper such as the New York Times does not "push an agenda" is ludicrous. And, one wonders who WP considers acceptable to perform the fact-checking function described in the last sentence. Mainstream media sources very rarely criticize or try to poke holes in other mainstream media sources' reports. Reporters and editors working for the same source very likely have the same POV.
Who does that leave to do the fact-checking? Why, none other than those self-published sources, the ones that WP finds unacceptable.
 For just one example, as of January 2007, neither the Washington Post nor the New York Times had mentioned the "North American SuperCorridor Coalition", the group described here. Despite that, it has its own entry at WP: /wiki/North_American_SuperCorridor_Coalition The original author of the entry admits that he took the information from NASCO's website and, while he does suggest adding more criticisms, that section as of February 2007 is quite anemic and does not contain any links such as the last.