Google Labs India introduced an online typing tool in Hindi. It is basically Indic transliteration tool , for eg if you type 'aaj mein upar' , This tool will convert that english text in to phonetic hindi as ' आज में ऊपर ' .
It also has an online dictionary based support which suggest you the relevant word as you type.
Its Interface is very light so that you can use anywhere, any kind of plugin support is not required in the browser.
So enjoy writing in Hindi without knowing to type in hindi.... :) click here for the tool