There's not a mobile version yet, as I was waiting for a new version of the forum software to be released which comes with a built in mobile theme. I've taken a look at the new version and it's full of loads of bugs and doesn't deliver on the functionality it was supposed to, so I'm holding off for even longer (if it ain't broke, don't fix it, etc...!)
This was requested a month or so ago and thats when I did some digging for more info. If it looks like the forum software update could be a while away, then I may be able to work something else out if it was a popular request.
Which phone do you have? I browse the forums quite a bit on my iPhone and it works great