I first learned of Kathryn Rose, an Anglican and a (church) musician in London, from her work to organize worship outside St. Paul's, where the Occupy London encampment is. (For reasons I don't quite believe, St. Paul's is closed for health and safety concerns.)
She also runs a free culture/liberal license project call Psalter Commons, to gather and encourage the composition of metrical psalms. These are the psalms recast as poetry in meter, and so can be sung to hymn tunes, erm, psalm tunes.
In case you ever wondered what "Old 100th" was in the hymnal -- it was the old tune sung to the metrical version of Psalm 100. Got it?