I have been always trying to improve my Mandarin, but that's not easy since all of my friends mostly speaks in Hokkian, I don't really have the chance to practice Mandarin until I finally started to play around with Google Translate.
Guess what, now my Mandarin improved a lot and now i can even text my friends in Mandarin (thanks to whom ever created Pin Yin).
For those who wants to learn Mandarin, Google Translate is a good start and of course you still want a dictionary for further explanations.
p/s: try get a girlfriend from China, It will definitely help a lot with your Mandarin. :)