There are squillions of them. With Bach alone, most of his organ works have been transcribed multiple times. If you look on the "transcriptions" tab of any of them on IMSLP you'll find an extensive list. Busoni is my pick of the transcribers - he actually wrote a treatise on the subject - but Liszt, Reger, Tausig and many others are also pretty damn good.
What are some well known organ works that possibly have been transcribed for piano? all i know is the d minor toccata >>"