Highway Feature of the Week
Large archive of maps and descriptions of unusual or complicated facilities, primarily in the United States. http://www.gribblenation.com/hfotw/
The Echelon Interchange
Professional paper on this part-at-grade, part-grade-separated intersection.[PDF] http://www.miller-consulting.com/echelon.pdf
SPUI's SPUI list
A list of single point urban interchanges, a fairly new type of interchange. Includes information on what a SPUI is. http://web.mit.edu/spui/www/spui/
WhereRoadsMeet
Contains aerial photographs and descriptions of unusual or complicated facilities in the United States. http://whereroadsmeet.8k.com/
Michigan Left Turn
Describes how this unusual intersection feature works, including history. http://www.michiganhighways.org/indepth/michigan_left.html
Museum of Dumb Highway Design
Aerial photos of and commentary on various interchanges which the author finds unusual or substandard. http://www.weathergraphics.com/tim/dumbroad/
Interchange of the Week
Detailed entries for locations in the Ohio River Valley, using aerial photography. http://www.ohiovalleytransit.com/page.php3?page=interchange_week/index
Interchange Diagrams
Interchanges in Florida and New Jersey, U.S. http://web.mit.edu/spui/www/int/