I hook up two usb 3 drives to my mac book air when I offload pictures, is there a way to get an extra usb 3 port through thunderbolt (to which i could connect another reader) or any other option to get dual or more SD cards read at the same time ?
You might want to take a look at this:http://www.caldigit.com/thunderboltstation/
It sells for about $200 US.
You might also want to consider a USB 3.0 hub. They are not very expensive and, even though the USB bus is shared by the attached devices, you should get reasonably good performance.