Just get liability insurance for your second car, so you're covered against damage caused to someone/something other than your own vehicle. Personally I don't see much point in paying a bunch extra against anything happening TO your second vehicle if its an old broken down thing. If it got stolen, or really horrendously broken, its going to cause more insurance hassle than worth in my opinion.
I've got my main car fully insured, which is no problem, but my second car i hardly ever drive. We live in a rural area, and this car mainly gets used on the farm. Any ideas on what my insurance options are for this one?