virustotal.exe is a small standalone application that does hash searches of scanner results on the VirusTotal website. It runs in single-file search mode or bulk hash-lookup mode.
It's integrated with the features in shellext: when you register the shell extensions, it adds a "VirusTotal" right-click menu item in Explorer for all files. The Hash Files dialog also has a menu item to run a bulk lookup on all rows in the listview.
The executable can also be run directly via its command-line switches, or by double-clicking it and loading an MD5 hash list from the clipboard via right-click on the main form. See the source for full details.
Since the VirusTotal public API has a maximum request interval of 4 seconds between requests, this application includes a cache feature where reports are cached to disk for immediate results on repeat lookups.