I love this website. The owner Paul Gardner has made accompaniments to much of the standard student repertoire for violin. The list is quite extensive and his playing is wonderful. Not midi!!

Youtube channel with piano accompaniments.

This company makes books and practice CDs for scales and violin literature. The Cds feature slower practice tempos and real orchestral back up tracks.

Most other Suzuki volumes are also available with an accompanying CD.

Large repository of backup tracks for fiddle tunes.