We use a church management system.  Go here and check it out.  There is an online demo.  Its very reasonable in price too.  http://www.glxyinc.com/

We have this same issue at our church.  Although there may be a better way to do this, the steps we have taken are to stagger the schedule making.  One ministry makes their schedule then the next ministry looks at that schedule and makes their schedule accordingly and so on... The most flexible ministry schedules last and this master schedule is maintained through the church office.  This has made a big difference in avoiding the overlapping of members serving on Sunday mornings.  It does take cooperation on the part of those making the schedules but it works for us.

We have used a program called SmartRoster for many years www.smartroster.net.  You can try it for free for 45 days.  Our church has been using it for about six years. I believe it is an upfront cost then an annual license fee (the fee for our church is about $80 a year). It is worth every penny.  We have one person that oversees the database...me.  We were able to import our names/addresses/phones and email addresses from PowerChurch.  We then set up the areas we needed.  We have a larger church.  We have about 1000 names in our church database now with SmartRoster.  We schedule for two services (some areas 3). We schedule for two areas of nursery, five other morning children's programs, ushers, greeters, and security.  We can schedule families together on the same week.  Our volunteers tell us when they are not able to serve (via email).  They LOVE this.  We send out email reminders to volunteers a few days before they are to serve. When looking to fill a holiday or needing more volunteers, our response rate to email is so much better than a bulletin announcement.  I hope that helps.  Would be happy to talk more to you if you need more info.  The support at SmartRoster is great.  I hope that helps!

We ran into the same issue.  We don't have a church secretary to manage all this so it was a huge task.  

We have used two things to really streamline things and found both helpful.  They are free.

1) Send out a form to all volunteers on a quarterly basis before we create a schedule.  We use a Google form that we send out to all our volunteers asking them when they are available.  Their responses are automatically recorded in a spreadsheet.  So we have all the info at our fingertips when making the schedule --way easier than what we were doing and people don't have to switch as much.  Here is a blog I wrote a while back to explain what we do with a sample form (I shared this with local pastors).  This saves the amount of time that the main scheduler has to do things.

2) Service Builder: This is a free worship planning site that has a song database and has added some really cool features for volunteers.  Multiple people can schedule and it will highlight if a person is schedule for multiple tasks.  Another cool feature is that it can automatically email or text (they have to set it up) people to let them know when they servce.  We use it for attendance too.  I just wrote a blog about this as well that has more info.  I wrote it because my main issue with ServiceBuilder is you can't see much without creating an account.  I tried to put up some images for people to see.  I have let other pastors from our Classis join our church's account to check it out in more depth before they create their own account.  Would be willing to do this for others too!  Message me directly and I can set it up for you.