OFFICIAL PAGE: Vocali.se
Vocali.se is a free web-based service for Deezer Research's Spleeter application. It allows you to upload a source file which will be separated into 2 stems (Instrumental + Vocals). The service accepts MP3/M4A/OGG/FLAC/WAV audio file formats with a file size of 20MB or less and a maximum length of 10 minutes. The service is currently offered free of charge, although donations are most welcome through PayPal.
Screenshot courtesy of Vocali.se