Assuming that all of your addresses have 5 digit zipcodes and 2 character states you can use a combination of mid, right, and len formulas to do this quite easily.
The following formulas start with addresses in cell A2
Code:
For the City: =MID(A2,1,LEN(A2)-9)
For the State: =MID(A2,LEN(A2)-7,2)
For the Zip: =RIGHT(A2,5)
Let me know if that works out.
Thanks