I am super late to mention this, but we use sendcutsend also, great results. For 3D work, was surprised not to see https://www.hubs.com/ mentioned - used to be 3DHubs. US and international multi-axis machining, 3d printing, etc. Quite helpful.
OSH Cut (https://oshcut.com/) provides similar services. Their automated DFM analysis software is pretty impressive.
Perhaps more interesting to the audience here is that Caleb Chamberlain, the CEO (and a college acquaintance of mine), writes a series of articles about running the business for the trade publication The Fabricator. You can find them here: https://www.thefabricator.com/author/caleb-chamberlain. He covers both business (operations, strategy) and technical aspects of running a highly automated small job metal fabrication shop.