I used to work for a FedEx feeder, and the pay was similar to passenger regionals. The work, however, is completely different. I usually worked four days a week, same run, seven hours of duty with four hours flying. I had every weekend and holiday off, and the same captain all month. We also got one long weekend a month, and captains get a week of every month. You stay up all night, or sleep during the hub turns if you wish. They even had a cafeteria and company store open all night. It was fun, but I wanted to try something different, thus the jump to pax. Hope this helps you.
Probably the biggest that I can think of is Mountian Air Cargo, they fly F-27s, C208 and I think SD330s, for FedEx. Others include Superior Aviation-Metros for UPS, Wiggins C208s for FedEx and BE99s for UPS, Air Cargo Carriers flys SD330s and SD360s for the Post Office. I flew EMB-110s for a smaller company that flew UPS freight. Pay was poor at best, I worked four days a week and flew about 1.5 a night and was on duty sitting in a UPS crew room for about 10 hours a night. I had no benefits, the equiptment was old, and we had to unload our own freight. At my pax regional the people load themselves, I have great benefits, I fly a nice new jet, travel passes for me and my family, and I make a little less money as an FO holding a line, than I did as a Capt flying freight. Not all freight companies are this poor, I just worked for a bad one.