Toastmasters is a sandpit to improve speaking to audiences.

You talk about anything you want, and each speech has an objective to improve your overall delivery. There are also lots of other speaking parts to every meeting to make it a success in it's structure, energy, and learning for everyone.

It also lets you try out roles in the organizing of a club.  The members take roles periodically, which together runs the club. So you can try out advertising, or branding, or event organizing, or teaching, or leadership - all the angles to running any organization - and roadtest your ideas for building the club. 

Sure, not everything about Toastmasters is great, and it's not the answer to every speaking event. But its good at bonding a mix of people with the aim of being better communicators.

If you're thinking of it, it's well worth the effort.