This Sunday (May 22nd), I visited A Church of Christ in Petaluma, located at 370 Sonoma Mountain Parkway. Ray McClendon is their pastor, a wonderful man. They have a regular attendance of around 50.
One thing you immediately notice at a Church of Christ - they use no musical instruments for worship. They sing all their songs a cappella, without musical accompaniment. It takes a little getting used to (if you have always gone to church where worship is accompanied with musical instruments), but I was unusally surprised at how good the congregation sang without musical accompaniment - usually in 4 part harmonies. It might be when you have no instrumental accompaniment, you tend to focus more on the singing.
The Churches of Christ follow this tradition because they believe the early Church did not use musical instruments, and because they do not find musical instruments mentioned in the New Testament. There seems to be evidence that the early Church either did not use musical instruments, or at least there is a lack of evidence of using musical instruments.
The Churches of Christ trace their history back to the Restorationist Movement, led by Barton Stone, Thomas Campbell, and his son, Alexander Campell in the early 1800s. (So sometimes it is called the Stone-Campbell movement). They wanted to return the Church to the practices and beliefs of the early church.
A Church of Christ in Petaluma celebrated their Jubilee (50 years) last year in 2010. They used to be at 520 S. McDowell (which is now Suzanne's Dance School). They moved into their current facility in 1994.