I am fan of VirusTotal service. I use their desktop app which lets me scan for suspicious file using multiple antivirus engines in one go.

The company has just announced that Google is acquiring them. They would continue to offer their products and would maintain their existing relationships with security companies.

VirusTotal said:

VirusTotal will continue to operate independently, maintaining our partnerships with other antivirus companies and security experts. This is an exciting step forward. Google has a long track record working to keep people safe online and we look forward to fighting the good fight together with them.