Hymnary.org

Hymnary.org is a database index of over 5000 hymnals and includes more than 1.1 million published hymns.  It allows you to search or browse hymns by title, tune, meter, key, scripture reference, and more. This is an invaluable site if you are searching for hymns or songs for worship, or if you are researching a particular hymn, or are looking for a specific musical arrangement.

For example, you can easily find multiple scans of "The Church in the Wildwood" from various hymnals by typing "wildwood" in the "text name" search box:

For some rather quirky offerings of hymnals, search for "poor Robert is crazy", or "naughty little mouse",  or "great ugly spider".

You should also check out the hymnary widget page http://www.hymnary.org/widgets , with its iPad app, hymnal comparison app, and search app  (which allows you to map texts over time by graphing the frequency particular words and phrases appear in hymn full texts across the years. For example, you can see the relative frequency of the words "death", or "heaven", or "hell"  over time.

The site was developed by the Christian Classics Ethereal Library and the Calvin Institute of Christian Worship, with funding from National Endowment for the Humanities grant.

For a thorough, intelligent review of hymnary.org, see David Mayo, "Web Review: Hymnary.org  - A Comprehensive Index of Hymns and Hymnals,"  Theological Librarianship 5, no. 2 (2012):4-5.