[dwich]

Sure, here's the ones I know of:

Quest-only: DirectLabs, Personalabs

Choice of Quest or DirectLabs: Walk-in Lab (switch the radio button to Quest on the category pages, and make sure a "QD" icon shows up next to it in your cart), TrueHealthLabs (make sure the tests you look at say Quest is an option), HealthTestsDirect (make sure the test list page is toggled to Quest at the top)

DirectLabs and Walk-in are generally cheaper than the others I mentioned.

[absk82]

You can try labespy.com. It will search for the lowest price amongst all these sites, amongst many others. You can find vitamin d for $33.