For JS Bach's organ works, the recordings by Helmut Walcha are something special: the texture is delightfully light and streamlined, giving it a special "chamber music"-like quality. Try the
budget 2-CD set if you're not ready to plunge into the 12-CD box.
A lot of baroque music features the organ prominently; try out for example Corelli's 12
concerto grosso op.6.
In the classical/romantic period, the organ is mostly used in religious music, but Lizst has written some works that are fairly famous. I love the rendition of Jennifer Bates on the label ASV, but seems that these are not available on Amazon.
Jennifer Bates is also one of the prime exponents of Messiaen, and before the appearance of the Latry cycle (which I have yet to get), her cycle was regarded as the best. The Bates's recordings also benefit from excellent write-up material important in understanding these somewhat unorthodox works.
Czech composer
Petr Eben is another modernist writing extensively for the organ, and like Messiaen, his inspiration is primarily biblical. His music is somewhat more approachable than Messiaen's, and he is as likely to write miniatures as long cycles. Nevertheless, the music is colorful and very individual. So far
Hyperion is the only label championing his works (try for example the ten brief
Momenti d'organ and the organ cycle
Job)
Oh, don't forget Ligeti's
Volumina if you want to blow your mind out.