www.google.com/ta3reeb/

Google ta3reeb (Arabic transliteration) offers an option for converting Roman characters to Arabic characters. This lets you type Arabic words phonetically in English script and still have them appear correctly in Arabic. Note that this is not the same as translation — it is the sound of the words that are converted from one alphabet to the other, not their meaning. For example, typing “ta3reeb” transliterates into Arabic as: “تعريب“.