When preparing worship, local preachers in our church have found some of the following sites helpful:

Bible

Bible Gateway
A searchable online Bible with many versions and in many languages

Revised Common Lectionary
The Bible passages for each Sunday in the lectionary along with links to Art and Prayers.

Hymns

Singing the Faith Plus
A companion site to the new Methodist hymn book “Singing the Faith”. Along with various indexes, the site enables to you search for hymns using a large number of search terms/catergories and provides hymn suggestions for the lectionary readings each Sunday.

Oremus Hymnal Wiki
A database of hymns which can be searched by title, tune, metre, theme, author etc. Sound files are currently not included.

Hymnal.net
A searchable database of new and old hymns and songs. Includes sound files of the tunes.

Net Hymnal
A searchable database of hymns. Includes sound files of the tunes.

Hymn Site
A searchable database of hymns. Includes sound files of the tunes.

If you are trying to find the music to a particular hymn, it can also be worth having a look on YouTube.

Sermons

The Text This Week
An online lectionary with links to commentaries, sermons, images, prayers etc.

Desperate Preacher’s Site
This site includes the lectionary along with sample sermons, a forum and other features. But many parts of the site can only be accessed with a subscription.

Sermon Central
Search for sermons by Bible passage or theme

Sermon Illustrations
Sermon illustrations listed by theme

Worshipping with Children

Talks to Children
Submit and read children’s talks

ChildrenSermons.com
A list of children’s talks on a variety of different Bible passages

Assemblies
Ideas for assemblies which can of course also be used for children’s addresses

Family Worship
Resources to help plan all-age worship

Family Friendly Churches Trust
Courses, resources, IT help, downloads and Holiday Clubs to support family friendly churches and worship. The IDEAS part of the website provides access (against a small fee) to many ideas and digital resources for leading all-age worship.

Kids Sunday School
Activities and ideas for Sunday School

Images

Google Images
Online image search

National Gallery
Many of the National Gallery’s paintings are available online.