CRJ200 Captain reports two different tugs failing to yield to his aircraft as he is attempting to taxi after pushback at CLT.

Narrative

After pushing back from gate we were about to commence taxi when a tug drove within 10 FT of the nose of the aircraft; from right to left; and it occurred as I was making the left turn off the gate. The tug had a red number 4 on the back and was towing 3 empty bag carts behind it. I applied the aircraft brakes and called the Flight Attendant to make sure she didn't get injured; as she was doing the safety demo and standing up at the time. I reported it to Ramp Control as well as Operations. As I was reporting it another tug drove in front of the aircraft; this time from left to right. The tug was so close that I could clearly see that the driver was not paying any attention to the aircraft. However; the number on the second tug was too small to make out. I again reported to Ramp Control. Although only the first tug driver made eye contact with me and the First Officer; neither one made any attempt to slow down or give way to the aircraft. The ramp personnel operating on the CLT ramp have no regard for the aircraft or other vehicles moving about. I would also speculate that they don't follow any sort of speed limit requirement or recommendation; although from what I have seen lately I don't know if CLT even has a speed limit for ground vehicles.