Yahoo!'s MyWeb which was announced in late April has now hit the main stream Yahoo! Search SERPs page. I personally did not notice the change, since I am logged into Yahoo! on my main browser and the MyWeb. So when you do a search on any term, for example myweb, you should notice (even when your not signed into Yahoo!) two new options, "- Save - Block".
Forum discussion, mostly positive at WebmasterWorld.