Go to http://mbeta.newsgator.com/d on your cell phone via the browser.
Download the appropriate client for your phone (if it’s missing or doesn’t autodetect, please leave a comment here and my friends at NewsGator will work on tuning it.)
Run the app. If you have a NewsGator account, you will log in and automagically see your feeds. If you don’t have a NewsGator account you will be prompted to create one and then you are off to the races.
I just tried it on my Dash (Windows Mobile) and it worked flawlessly.
Once all the kinks are worked out, this will move to http://m.newsgator.com/d
God these guys are good.