Make your store accessible across different geographies with Language Translator from Biztech. It’s an ideal extension for customers to view products of your store in their regional language. It will allow you to manage multilingual stores more effectively and target a wider customer base. With Magento Language Translator admin can easily search and translate any string(supported by your store locale settings) from the store. With Language Translator admin can translate Products, CMS Page Data, Static Blocks, Product Reviews and Tags with Mass Translation.
you can create your own module for translating language. Just follow below link.
you can use inline translation by enabling translation from admin. Just follow below steps
go to admin panel->System->Configuration->Advanced-> Developer->Translate Inline
this is the best way because if you use other extensions it may cause on your site performance.
enjoy magento !!