Edward's advice is excellent. Also, keep a copy of passwords, and other log in information so that if your web designer forgets/ leaves the church/ gets run over by a truck, you have the ability to maintain control of the website.
Put pictures of people on the site. It helps give the impression that people actually attend your church, which is always helpful. Also, put a picture of the pastor with his bio. If he is a severe-looking man, put his wife and kids in the photo to mellow it out.
The most useless websites are those that do not tell where the church is or what time it meets, have only one photo of the actual church building and none of the people (or especially those with no photos at all or random landscape photos), are not updated regularly, or the church has lost control of it entirely because the designer moved to Outer Mongolia to realize his dream of herding yaks.
And I have said this before, but I will say it again: update the website. If the church moves to a new location, change the address and directions on the website. If the church gets a new pastor, change the bio and photo. Don't leave pictures of people who have left the church on the site (it depresses all current congregants when they go to the site and see a huge collection of photos of everyone who used to attend). Don't leave announcements up from three years ago--it makes it look like your church has died.
But a well maintained website is an excellent tool for any church, and these days, a lot of people won't attend without checking it out online first.