When dealing with an unfamiliar website / web business, I use these tools to research the site's reputation and scan for malware.
These checks are quick--they check the URL against blacklist databases and URL reporting sources. Enter the URL and get the rating.
AVG Threat Labs
Norton Safe Web
TrendMicro Site Safety Center
WatchGuard Reputation Authority
Web Of Trust
This one combines reports from several reputation-checking sources.
These checks are more comprehensive, but take longer because they actively scan the site for malware. Enter the URL, and it will be scanned.
Comodo Web Inspector