If your user group becomes moderately successful, you may find yourself overwhelmed by the number of tasks that it takes to keep all the balls you're juggling going. As your life becomes busier, it may be difficult to pay attention to the small things that your user group needs - updating web pages, reaching out, etc.
If this has happened to you, the answer is obvious: ask for help.
What may not be obvious is how to do ask effectively. From my experience, it doesn't work to simple send a broadside, especially in a user group setting - "I need help, if anyone wants to get involved, please let me know." This is a good first step, in that it results in you admitting that you need help, but it's unlikely to be effective. From that pitch, your members see none of the benefits of volunteering and all of the costs.
So how do you get the help you need? There are several options. The first is simply to ask people personally for specific favors. When you ask someone personally for some specific thing, taking into account their skills and connection to the group, it is much easier for the person to say yes. So I've found that by splitting up the upcoming meeting into small tasks that I could request from people who have attended multiple meetings and shown their interest, we are able to manage the meeting even as my personal life has gotten much busier.
But if you need long-term help, you may need to turn to other methods. One possibility is to formalize your organization, with a mission statement, treasurer, etc. In that case, you can hope that people will volunteer for the positions, and accept the obligations that those positions create. Transitioning to this sort of formalized system isn't one where I have little experience (although I've been involved with them), and I'd love to hear stories about making that transition work.
Whether you create such a formal structure or not you'll have to sell the volunteers on volunteering. So don't forget that helping to organize a tech community _does_ come with real advantages! You'll have to figure out what advantages your group has, but whatever they are, you should remember to mention them - people have to be choosy about how to spend their time so you need to sell people that they're going to gain something from the process, or if you can't promise that, then at least promise fun.
And really, I think organizing a user group should be both. That's why I do it.
P.S. One other way to avoid being overworked is to only grow your user group based on your member suggestions. Pare down your group to what you can manage, and then encourage anyone who wants to do more to take their ideas and run with them with some support from you. If any members of your group have energy this can be one way to grow your group in a way your members are by definition going to like. Your job becomes then becomes that of a facilitator to a self-organizing group. Sounds nice if you can get your group to do it - and it works for NextNY.