With FHA financing just 3 years after a short sale (with late payments) is needed - if your mortgage payments & other debt payments were on time for the 12 months leading up to the short sale, and weren't behind at the time of short sale, then you could've refinance with FHA right after the short sale (no wait).
Conforming (Fannie Mae/Freddie Mac) financing requires 4 years after the short sale and then 90% loan-to-value financing is possible, or after 2 years and prior to 4 years, then refinancing to 80% loan-to-value is possible. After 7 years then maximum loan-to-value is possible, currently 95%.
If your current loan is owned by Fannie Mae or Freddie Mac, you may be eligible for a HARP refinance, and if you go back to your same mortgage servicer for the refinance, they are able to waive short sale, bankruptcy & foreclosure waiting period requirements. However a different lender than yours would not be able to waive short sale, bankruptcy & foreclosure waiting period requirements, as those more lenient guidelines are only for "same servicer".
To check if Fannie Mae owns it: http://www.knowyouroptions.com/loanlookup
To check if Freddie Mac owns it: http://www.freddiemac.com/mymortgage/
Shane Milne | Lending in all 50 states | NMLS #81195