You could buy a Prepaid SIM from Telering or one from Hofer (=Supermarket Discounter, austrian version of ALDI) which are 7 ct/min to
austrian landline and all other austrian networks.
Then use
DialNow | Cheap International Calls
The SIM will bring you for 7 ct/min to Vienna landline, Dialnow will connect you from Vienna to i.e. USA for another 0.5 ct/min.
Dialnow is a Betamax brand and can be used worldwide. The only important thing is a cheap access to the landline of the country in which you are.
You can save your phone numbers complete in your phone memory, separated by a p (pause) and dial directly from the memory, or you can send the destination no. as a DTMF also.