There's an unsupported web interface that was done back in the dark ages before development on the iPhone and iPod touch was opened up. If you can leave a computer running OmniFocus with connectivity to the outside world, you can get a context view of your actions and inbox and check items off, add items to the inbox, and so on from any decent web browser. Using it will probably not impress anyone unless they are a Ruby hacker ;)
You can find it on Softpedia
here.