With the Tesla Roadster being derived from the platform of the Lotus Elise, it's worth remembering that the Elise itself was developed as a modern successor to the original minimalist Lotus 7. Colin Chapman originally started building 7s fifty years ago and eventually sold the tooling to Caterham cars who continue building cars based on the design to this day. Over the years, a number of other companies have come and gone building sports cars inspired by Chapman's original.
Aside from Caterham, the most successful has been Westfield. Westfield is currently developing a battery-powered race car to be used for a single make club racing series. The 600kg racers will be equipped with lithium ion batteries with enough capacity for a typical fifteen lap club race. On Jan. 10, 2008 at the AutoSport International Show in the UK, Westfield will launch a design competition where high school and college students can compete to design the body work for this new racer. The winning design will be developed by Westfield and displayed at the 2009 AutoSport show. The race series could start in 2010.
[Source: Westfield, thanks to Domenick for the tip]