There are a fair few sites popping up testing for this issue. I know this is possibly overly motherly, sorry, but be careful. You may not know who is running the site, what they are actually testing for and what is done with the information collected. Consider sticking to the main sites and known security organisations.
Metasploit now has a module out (https://github.com/rapid7/meta
Not saying the free scanners are "evil", just saying be careful what you use.
Cheers
Mark H