I use FedEx. They tend to be cheaper and faster than UPS or DHL.
I go to tire and wheels shops for boxes, pack em up myself, then off to a FedEx center for the labels and send them out.
EDIT
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Did you sell your OEM 13"s?
If those are the wheels in question finding a wheel box that size (if you took the tires off that is) might be tricky! But removing the tires brings down the shipping cost dramatically. Shipping for all 4 should be around $40. I sold a set of BMW 13x5.5 from Montgomery, Alabama to Somewhere, Michigan a couple years ago for around that.