Like ArchDaily, the rankings are based on Alexa, so I could use one resource for compiling the below list of 66 English-language websites*. The rankings are based on Alexa's Global Traffic Rank for July 11, 2011; their rank is a measure of a site's popularity over the past three months based on the combination of visitors and pageviews**. A more thorough ranking may have taken other things into account (Facebook fans, Twitter followers, RSS subscribers, etc.), but I'll leave that to somebody else willing to spend the time and effort on such a list.
A website was considered for inclusion if architecture is either its main focus or one of its major subject areas; this is not meant to be an exclusive list, but one that acknowledges the presence of cross-disciplinary writing and browsing online. Therefore design sites are found alongside architecture sites. The websites are categorized and presented below in a sortable list; just click on the black-bar heading to sort alphabetically by website or type. The types are defined as follows:
Blog - Architecture: Weblog or eZine authored by one or more people focused exclusively on architecture.
Blog - Design: Weblog or eZine authored by one or more people that looks at design in general, featuring architecture among other disciplines.
Competitions: Listings of architecture competitions and related topics.Database: Fairly exhaustive listing of buildings.
Forum: An internet message board where registered users can post comments in subject threads.
Organization: The homepage of an organization related to architecture.
Profiles: Listing of architect and related profiles.
Publication: Online website of a print publication.
Social Networking: Social media platforms featuring user-generated content.
*66 because that is where this blog lands, and that number also happens to double that of my sidebar list of 33 favorites, which this list will supplant shortly.
** For reference the #1 site above is ranked 1,550 at Alexa (Google is first of all websites), while my blog, #66 is ranked 251,360.