Other good sources of auto/boat electrical parts I always forget about:
Genuinedealz does free shipping, and their prices are great. They will make custom cables, too, for a $1-per-connector labor charge. I remembered about them tonight, right after I spent more than I should have for some Blue Sea stuff on eBay.
Summit Racing does have good pricing and selection on Weatherpack connectors, among many other things.
Del City Wire has reasonable prices, and they (very) occasionally do free shipping on small orders. Memorial Day weekend is apparently one of those free-shipping occasions.
Susquehanna Motorsports makes very good headlight harnesses, and is a good source for all things Hella (including E-code headlight housings). And all things rally-related, of course, from WRC-spec mud-flap material to Hans Devices.
To be edited as I remember or discover more…