Hi,
One use that car headlights may be good for is as diversion load, though I'd prefer to use water heating elements as diversion load.
I regularly use car headlights (12V/55W (5amp)) for testing power-supplies and smaller batteries (e.g. 7Ah). 2 weeks ago I converted an old PC powersupply from 12V to 13.8V (not very easy! involved disconnecting the +5V, re-wiring the stabilization loop (to +12V instead of +5), changing overvoltage protection, etc). Anyway, the PSU should be able to put out 13.8V at 10 amp. Just grab an old headlight (with the dimlight burned out), connect it, 5 amps! Connect another one, 10 amps! etc. One problem: it's difficult to read your DMM with all that blinding light X-)
So, my opinion, they're fine for PSU dummyloads and automobiles. For alternative energy, perhaps as diversion load, but not as main lighting, unless you've got more power than you can use (yeah, right...)
Grtz,
Peter