This service came to my knowledge moments ago while reading Prevx 4.0 beta release date thread. I scanned 46 malicious URLs with it, and it flagged them all either with Suspicious, Moderate Risk and High Risk and never once it gave them a green rating. Here -http://brightcloud.com/solutions/allapps.php you'll find extensions for Firefox and Chrome. Some of you may find this useful. In the short test I performed was accurate.