Localphone rocks. If you have a high volume of international; calls, you can also try Localphone affiliate Voxbeam.
I use 1. Google voice- 2 accounts ,domestic calls
2. Localphone most international calls, Us and foreign DID
3 .Callcentric with free NYC DID for 911 service, some international calls, calls where I need features
like 3 and 4 way calling and/ or superior call quality