I know that you can import from Facebook to Yahoo, and from Yahoo to Google+, but is there any way yet of importing followers and following to Google+ from Twitter?
I wrote a tool to help with this. It can find the Google+ profiles of folks that you follow on Twitter.
It does rely on those you follow on Twitter having a www.gplus.to Google+ nickname that matches their Twitter name.
Currently it will find around 20% of those that you follow, but this can be increased simply by spreading the word, e.g. via tweets, that Twitter users should go and grab their matching gplus name.