Bitcoin Wallet, the popular wallet for Android and BlackBerry, is also used in Greece a lot. However, it's not completely localized. Would you like to help out? You will be translating from English to Greek, on Transifex:

https://www.transifex.com/projects/p/bitcoin-wallet/

If you create an account there, you can start right away. You are contributing to free software, GPLv3 licensed. Thanks!