Hi Victor,
For my first year of organ study the teacher had me start out on the Eight Little Preludes & Fugues. Even in present time, 48 years later, I still enjoy those pieces, and so does my congregation - those are the ones the most people hang around to hear.
You could also try some of the Bach Chorales. One of our members has posted many of those chorales in
this thread, and are there for the taking.
Indeed, I use Jesu Joy of Mans' Desiring periodically ... one of things my teacher taught me on that piece was not to retard at all at the ending, save for the last two chords (D7 and G major). If you play it this way sometime, you will feel the rhythm continuing on while holding the final chord for a few seconds.