Also, if you live in a muddy place in a cold and wet climate, you become obsessed with the idea of remaing self propelled without becoming unbelievably dirty.
Incredibly, a book has been written to cater to even this interest, Folkhemmets farkoster - Om Cykelbilen Fantom och andra fräsiga hembyggen. It is beautifully written and illustrated. The author, Claes Johansson, even builds the cyclecar "Fantom" himself.
In Sweden during WWII times were good compared to almost anywhere else in Europe, but still no joke. All cars were forcibly " borrowed" for the war effort. So people built their own. On the top here is Johansson's modern build of a model called "Fantom". As many as 100 000 plans for this velomobile may have been sold in Scandinavia during thirty years in print. Above is the extremely unfortunately named "Pedobilen". While the Fantom was made of plywood built around a steel tube frame, the Pedobil was built more like a canoe, with wood and canvas. Below is an excerpt of the plans for Fantom.
This swedish fad for velomobiles in the war years are what prompted danish CG Rasmussen to start making his modern-day version, the Leitra.
All pictures in this post taken from "Folkhemmets farkoster", Byggförlaget.
Update: You can still order the plans for Fantom here. In other words they have been in print for 65 years! The drawings do not seem to have changed since WWII. But you can also get the plans for free along with the book mentioned above.
Update II: Let me make clear, since this is one of the most popular posts here, that the "Fantom"-plans are extremely rudimentary. And the end result will be a very heavy vehicle. To me it seems the least expensive route to a velomobile is ordering the Alligt Alleweder kit from Dutch Speed Bicycles, or build something around plans at Atomic Zombie.
Update III: Well, the plans mentioned in Update I can no longer be ordered as of april 2011. A photograph of some of the plans can be found at Forum Brian. The text on this page states that while maybe 100 000 plans were sold, they were very vague and in the end people had to interpret them in different ways, leading to wildly different approaches and results.