I was inspired by this episode of SEOMoz's whiteboard friday where Rand talks about tracking non-traditional conversions (like when someone posts a comment on your blog) so I decided to check out how easy this was to do in Drupal.
By default, when someone submits a comment, they are redirected back to the node to view their comment (even if it needs approval first). This causes a problem because it doesn't really give us a unique URL to use as a goal in Google Analytics (unlike the webform module).
What you'll need to do is grab the great actions module which we will use to redirect the user to a custom thank you page once their comment has been submitted. And while thats downloading and installing, create a new page that will be the thank you page when users submit a comment.
Next, navigate to Site Configuration > Actions and create a new advanced action to redirect to your new thank you page click save. Now, just head over to the Triggers settings (Site Building > Triggers > Comments) and assign your new action to the "After saving a new comment" trigger.
Now all you need to do is setup the goal in Google Analytics and wait for the data.
Do you have any other non-traditional conversions that you're tracking? If so, what are they and how are you tracking them?