Composer Arlene Oost-Zinner has been distributing her a cappella psalm settings for a few years through the Chabanel Psalms project, and this summer she has brought out a complete set of responsorial psalms for Sundays and solemnities, published by the Church Music Association of America.
View the Parish Book of Psalms at Scribd
By way of disclosure, I contributed to the book by doing some custom chant typesetting so I’m pleased with how the music looks. (The Scribd display above is not exactly what the page looks like, but it’s close.)
It’ll be available from Amazon shortly:

In CMAA’s spirit of sharing, free downloads of individual psalms are available online at http://musicasacra.com/pbp/.