These sites let you scan websites for viruses and all sorts of malwares. They analyze the suspicious URLs and let you know whether they are harmful to your computer or not.
VirusTotal is a free online service that analyzes files and URLs enabling the identification of viruses, worms, trojans and other kinds of malicious content detected by antivirus engines and website scanners. At the same time, it may be used as a means to detect false positives, i.e. innocuous resources detected as malicious by one or more scanners.
Norton Safe Web is a new reputation service from Symantec. Norton’s servers analyze Web sites to see how they will affect you and your computer.
Enter a URL and the Sucuri SiteCheck scanner will check the site for malware, blacklisting status, and out-of-date software.
Unmask Parasites is a simple online web site security service that helps reveal hidden illicit content (parasites) that hackers insert into benign web pages using various security holes.
This is a commercial managed URL blacklist service. The bulk of the entries are downloaded from various free sites. You can search whether a site has been black listed or not, for free.