I'm ordering from this place
http://www.modeltrainsoftware.com/
You can get kits made specifically for Lego from this place
http://lifelites.com but they're too large for ecto-1, I'd have to drill through and modify bricks to use them. The above place has what's called "surface mount" (SMD) Chip LED lights which are tiny little things (1.8mm x 3mm) so I should be able to just stick them inside the transparent pieces without cutting or drilling.
Lifelites would probably be more useful for buildings as it'd be much easier to build in spots to put them as they're built inside of technic pins, for small things like ecto though it makes it much more difficult.
If I'm happy with this when it arrives I may try lifelights for lights for the haunted house, maybe spooky green lights inside?
It'd be awesome to have some lights inside and out the haunted house with a mini smoke machine (if such a thing exists?) spilling fog out the doorway.