If you login to Google Webmaster Tools and select "Sitelinks" under the "Site configuration" section you will be presented with a new way of managing your sitelinks.
In the past, Google would list your sitelinks and let you block them one by one. The thing is, the sitelinks didn't always match up with your real sitelinks.
Now, Google is showing you two boxes, one to enter the URL of your site for a search result that triggers a search result and another box for the sitelink URL that you want to "demote." Google explains to demote a sitelink URL:
- On the Webmaster Tools Home page, click the site you want.
- Under Site configuration, click Sitelinks.
- In the For this search result box, compete the URL for which you don't want a specific sitelink URL to appear.
- In the Demote this sitelink URL box, complete the URL of the sitelink you want to demote.
Here is a picture of the new interface:
Here is a picture of the old interface:
A WebmasterWorld thread calls this a "backward" change. But I am not too sure. The issue is that sitelinks can show up for different queries, different URLs on your site and so on. So maybe this might work better, but yet be a bit more confusing for the webmaster to figure out?
Forum discussion at WebmasterWorld.