[_ck_]

The approach Digg uses is very simple and would not need such an advanced plugin like “promote to front page”.

All you need to mimic Digg is allow voting on topics and then replace the part of your front page that shows the latest-discussions with the list of topics by highest rank.

In fact there is already a topic voting plugin that does that, you’d just have to edit your front-page layout. You could then go further like Digg does and restrict highest rated by date – 24 hours / 7 days / 30 days / all time