Google has been making all of their popular web-apps compatible with the iPhone. Let’s just think about google docs, google mail, etc.. The newest member of the iPhone compatible club is Google Translate. It’s not yet possible to translate full web-pages from within the web application. But if you quickly need to translate something then google translate is what you need.
For the people who haven’t migrated to firmware 2.0(1) yet, and you need a offline translate, i do recommend that you have a look at WeDict.
Google Translate link