If you want to use something other than the twitter banner, you can use the rss feed.

Ning sites have an rss feed reader box. On your twitter account, below those you follow, is an rss button.

Right click hit where it says open link in new window. When the link opens copy the link. Then go to your ning site, and paste that url feed into your rss feed box. Now you have a live feed of your tweets. Its another way to post your twitter. besides using the twitter widget.

Its a tick I just learned.