At this point most of what I own is more for lighting gags or practicals than anything else. I have a few lamp base sockets on cords as well as porcelain bases I screwed onto chunks of plywood. I've also recently found a local source for old-school AG-1, Press 25, and 22/22B flash bulbs. Got a few of those left from a shoot along with the wiring bits I used to get them to flash. Add to that a few handfuls of various Xmas lights, a halogen 250, standard dome clamp light (for the 22B flashbulbs) and some other odds and ends.
Just found some awesome 200w tungsten globes (Feit Electric, I think) for very cheap at Orchard. Love the light they give out. Going to do some test shots where I try the old "Single clear bulb exposure" challenge. These work great on the cheap-ish Ikea 300w dimmers that they have in their lighting department.
Also got an assortment of gels from various projects, a couple home-made bounce boards, etc.
Really only just beginning to acquire lighting stuff, I've been concentrating on the freelance AC side of life for a while but hope to pick up more DoP side projects in 2011. Even then there's pretty good access to g/e gear through folks I know, so anything I buy probably going to be supplemental unless the gigs I pull change and I need my own small kit all the time.
What I'd love to check out is this kit:
http://www.filmtools.com/rosco-litepad-quick-kit-29024000bkit.html
Realistically the "gaffer's" kit (12 lamps) is probably a better deal, but costs more. I've only seen the smaller versions, but the light is clean and oh-so-pretty. Punchy, but still soft and not quite directional, but not quite not directional either. Neat little critters.