Savko.com seems to be the best place for plumbing eqp not found in the local hardware stores and ground shipments get to me in 1 day.
The Menards by me (Naperville) doesnt stock bulkheads, but they have strainers and a wide selection of fittings, nipples, ball valves (even threaded) and hoses. They also stock unions, but only slip. The Lowes in Naperville isnt as diverse, but they stock true unions (slip). In my area, home depot easily has the worst plumbing section of the four (counting Ace Hardware).
Aquatic Ecosystems also carries anything that you need to plumb your tank.
