Site Checking

There are a number of sites that will check an URL for you to try and determine if it's hosting malicious code. Some of the ones I've found and use include:
1. Wepawet: http://wepawet.iseclab.org/ Wepawet will check a site for either malicious Java or Flash.
2. VirusTotal: https://www.virustotal.com/#url Though VirusTotal is most well known for it's file scanning service (running samples through multiple vendors AV engines to determine malicious executables), they also offer a URL scanning service as well.
3. Zulu: http://zulu.zscaler.com/ Zulu checks for phishing pages, obfuscated Javascript, suspicious domain names, SURBL blocks, parked domains as well as other checks.
4. Robtex: http://www.robtex.com/ Though Robtex is not a URL site checker per se, when you search on a URL or domain, Robtex reports rbls.org blacklistings and the WOT reputation, and pages for the site with Google Safe Browsing, McAfee Site Advisor, and Norton Safe Web.