It depends on how deep you want/plan to go

Here're some links to a few other threads that may have some info you might find handy:

Website w/ brief summary of Consumer Housings:
Website for brief sumamry of Consumer U/W housings - ScubaMagazine.net Forum

Equipment Insurance.
Equipment Insurance Recommendations? - ScubaMagazine.net Forum

Manufacturer housings generally are only rated to 100ft or so & vary in quality & range in price from $100-300.

If the manufacturer doesn't make a housing for your camera, & you can't afford/or get one from the big boys, ewa-marine seems to be the catch-all for everything else. But bear in mind that it is really a drybag with a lens welded on and won't protect your camera from pressure.

When you decide, my purchasing experience w/ B&Hphoto so far has been very positive.