I know I just wrote about Sucuri in January but I just found their free website scan: http://sitecheck.sucuri.net/
The tool will scan your site for malware, blacklisting, injected spam, defacement and a firewall. It will also give you basic details of a site – like the hostname, server, IP address, links and scripts.
So if someone called me with a wonky website – my new first step might be running it through this free tool. And if the tool found something wrong, I think I’d be looking at their fee-based fixit services