That's going to be a *really* complicated question to answer, because there are dozens of 3D printing materials which will all have different weights, and different printers running on different specs will likely output different at different densities. (particularly the FDM printers)
My suggestion: if there are specific materials or specific print bureaus you'd like to use, try contacting them to ask for some specs. If you're not sure what materials or bureaus you want to use... you'll need to do that before getting any sort of real answers. And if weight is super critical to you, you might need to order some test prints with known volumes and work out their densities for yourself.
If you're just looking for a really quick and dirty ballpark estimate, after googling some common SLS, FDM, multijet and SLA materials, you can expect a range of between .9g/cm3 and 1.3g/cm3.