Most groups have a small group of loyal attendees. These are the folks that should be stepping up to help you out. Most likely one of two things is happening -- either they don't know that you are feeling exhausted and overextended or they don't know how to help.
By talking honestly with this small group about your frustrations, you can open the door to solving the issues as a group. Also, remember that volunteering does not come naturally to many people; especially if the tasks that need done are things they've not done before. They may feel intimidated by what a good job you've done and feel they could never put together anything half as good. Look for small un-intimidating tasks that will help them get their feet wet or invite them to "help you" do some of the tasks that need to get done. This way they get involved, they become familiar with a part of the job you would like to delegate, and you get some immediate relief.