You'd probably like his 'Des Canyons aux Etoiles' and 'Oiseaux Exotiques'. hese are some of my favorites of his works. And the pieces already mentioned are good recomendations too, like the 'Quatuor pour la fin du temps'. He also wrote some song cycles, like 'Chants de terre et de ciel.' His piece 'La Transfiguration de Notre Seigneur Jésus-Christ' is cool too and requires a large orchestra and chorus.
There are some recomendations anyway. He has a relatively large and diverse oeuvre, so there's plenty of Messiaen to discover.