I'm thinking about starting a French horn ensemble this next school year, but I kind of need to find music that is entirely French horn parts. Does anyone know any music that has at least three of four horn parts?

Have you considered arranging some music which is out of copyright? New World?

You might try transposing some music. Choral (vocal? choral? I don't know how choral's spelled) music has four parts, soprano, alto, tenor, and bass, you could transpose a song you like and you'd have four parts to fill.

Thanks for the tips. Maybe I'll try that.