For more examples, consult the Directory of Open Access Journals, which provides a thorough list of peer reviewed open access journals.
The open access movement is a direct result of the current issues with the traditional publishing model. Open access publications are available online in a durable archival format and at no cost to a user. They are not under the same types of stringent copyright and licensing restrictions as traditionally-published articles.
Open access journals are, to their users, very similar to many traditionally-published journals. Like many traditionally published journals, they are accessible through a publisher's website, employ peer review to maintain the quality of article content and many are indexed in MEDLINE and Scopus. The main difference is that since these journals are not paid for by library or personal subscriptions, other models are used to offset the costs of journal production.
Most open access journal publishers use the "author pays" model, where the author of an article pays the costs for the article's editing and distribution. The article processing charge can be a few hundred to a few thousand dollars depending on the publisher and individual journal. A variation of this is an "institutional membership", where the author's institution (or, in some cases, institutional library), pays a membership fee annually. All authors from the member institution get their fees for accepted articles either reduced or waived.
A short video from PHD Comics explains open access publishing.
Many open access journals compare well to traditional journals with regard to impact factor. According to 2012 impact factors published by the Institute for Scientific Information (ISI), all seven Public Library of Science journals have impact factors ranging between 3.7 and 15.3.
Over half of BioMed Central's journals are ranked by ISI, with 88 titles earning impact factors of 2.0 or higher. The Journal of Medical Internet Research earned an impact factor above 3.0 for 2012.
Gold Open Access: Gold open access refers to immediate, unrestricted access to the version of record (i.e. the publisher's version of an article). An author publishes in an open access journal that offers immediate open access to all articles via the publisher's website. Some "hybrid open access" journals provide gold open access for individual articles where an author has paid an open access publishing fee. Despite some misconceptions, many open access journals still adhere to the traditional peer review process.
Green Open Access: Green open access refers to when an author archives a version of their work in an open access repository. Often these items are "pre-prints" (i.e. the original version of a manuscript that is submitted to a journal for publication, before it has gone through the peer review process) or "post-prints" (i.e. drafts have gone through peer review and have incorporated all revisions) rather than the publisher's version of record.