LINK
I've been talking autocross with an older guy I bought a helmet from, and he mentioned he is first in line for one of these kits. It's an 818kg (1800lb) mid-engined kit powered by a Subaru boxer motor. Looks like a LOT of fun.
It requires a single-donor 2002-07 Impreza/WRX with drivetrain, brakes, suspension, etc... and is intended to be a sub-$15k build.