Admin Team Meetings : Deskdemon.com Forums

Depending on how your office is structured, there are a number of things you could do...

I love the training idea and would certainly encourage that.
Have a guest speaker from one of your departments come in and discuss what that department does so your admins learn more about the company as a whole. Rotate between departments at future meetings.
Process improvement - discuss various aspects of your jobs, how things are currently done and what could be done better - review tasks for best practices and look for ways to enhance proficiency (how do you do "this" in your department - could cover things like mailings, travel, expenses, etc.) It's an opportunity to learn from each other for the future instead of just sharing updates. In particular, discuss frustrations (not talking about whining here, but identifying issues and opportunities for areas to strengthen) and brainstorm ways to make improvements.
Have a vendor come in and give a presentation about products or services that your company uses to highlight new features and trends in that industry (i.e. travel, catering, conference call services, etc.)
Review as a group areas where administrative professionals could suggest improvements to the company. For example at one of the companies where I worked, we developed a formal cross training policy where the admins would cover each other when out on sick, holiday, etc. and we also brainstormed an enhanced phone directory option.