Modernage is my usual lab, though one of the transparencies I got back today was scratched. In general, I've been very satisfied with them.

Duggal is big and does everything, but if you're not a big customer, they may not pay much attention to you.

MVlabs for B&W custom work. Kenneth Taranto is excellent--mainly headshots, but also fine printing. Clone-a-Chrome for Ilfochromes.