Because I know how to speak Cantonese but not Mandarin, and because I cannot read any Chinese, when I chat with girls on QQ, I use a combination of
Google Translator and
CU Vocal to help me. This is best done on a computer, rather than on a mobie...
What I do is I type into Google Translator what I want to say, it gives me the simplified Chinese text, I paste that into CU Vocal to hear it read out in Cantonese so I can verify it makes sense and isn't gibberish, modify the sentence further if it needs tweaking (swapping the words around to sound more natural or sometimes by going back to Google Translator to rephrase), then paste it into the chat box.
To understand the Chinese that comes back through the chat, I simply paste it into CU Vocal to hear it read out in Cantonese. If I still cannot understand it (which happens due to the Mandarin way of saying stuff being often different to Cantonese), I clarify by pasting it into the translator to get it into English text.
I've become quite adept at this now and the conversations are pretty fluid. I've even gotten a feel for the Translators so as to know how to phrase the initial English input to get more natural sounding translations out.
Babelfish also works for translation, and there's also
TTS which is another text-to-speech website, but it's not as useful for me since it only has Mandarin speech, not Cantonese.
And I know what you're thinking by now... The things I do to keep up relations, uh?!