Here's a setup that uses 2 free web services, and doesn't require any software running on your Mac.
1. Like before, setup Dragon Dictation to post to your Twitter account
2. Use
http://gtweetapp.appspot.com/ to create an RSS feed from your Twitter account
3. Use the free plan at
http://www.feedmyinbox.com/ to email new RSS entries to your +omnifocus email address. The caveat here is that the free plan only checks your feed once daily. If you want real-time, you have to upgrade to a paid plan. But for me, daily is just fine.
The bottom line is that it works with the really sweet workflow of dictating something quickly into Dragon, posting to twitter in 3 taps, and having it turn up in my Inbox the next day.