Nickname for Portland because of all the rainfall it receives. Puddletown has made its way into popular PDX culture, as it's commonly affixed to names of businesses, sports teams, et al.
The Polar Plunge is an event for the benefit of the Special Olympics during which participants jump into a swimming hole in Lake Monona. Since the event takes place in late February (February 20th, 2010 at Olin Park), the lake is always frozen solid. Only the bravest (craziest) of souls dare jump. For many, sponsoring a "plunger" is the best way to participate in this very Wisconsinesque activity.
A style of housing dating back to the 17th century, similar to a town home; very common in the older parts of D.C.