I am interested in laser diodes and diode modules that perform similar
to the ones in Black and decker laser levels.  I need them to be small
(.25 to 1 inch).  I need to know what is the lowest price i can get
(both for bulk and single purchases), and what companies supply and/or
manufacture.

Coincidentally, I have just purchased a couple of laser pointer key
chains for £2 each, marked down from £6. Come with 3 cells and 42
screw-in projection patterns. Total length is 2.5 inches but the body
includes 3 cells, switch, dropper resistor board, tip and chain tag.
Laser itself is about 0.75 inches. Current consumption with new cells
is about 40 ma and pretty bright.

Industrial modules are horribly uncheap -- £60 upwards. Foreign
imports and untraceable. Best source in UK is Indo-Asian ?bargain
stores?. Suggest you enquire in similar.

Best

can you be more specific.  Do you require a 5.6mm can?  What
wavelength do you need (650nm red?), what wattage or power (5 mW, 10
mW).  What qty?
Toshiba, SONY, hitachi make laser diodes, mostly for the DVD market. 
Given DVD storage densities, the volume (and therefore the lower cost)
is with blue lasers.  Some red for optical readers, laser scanners,
scan engines made by OEM's.