It's gonna be a CPO thread!
I recently bought the complete organ works of Franz Tunder and Nicolaus Hasse. I think it's part of the Northern German Baroque Organ Works series, mentioned by 71dB:
But I'm also happy with a Pachelbel CD of the series Süddeutsche Orgelmeister
, a production of Oehms Classics.
I think I'm falling in love with the German organ tradition. Alas, nowadays every love one holds costs money.
Nevertheless: I'll keep your advices in mind!