I organize a meetup in the Denver area,
Welcome to Denver Yorkies. Our charter is for playtime and socialization with dogs their own size. The meetups are a lot of fun. In the summer we meet at a grassy private school yard for free and at various doggy daycares indoor or outdoor the rest of the year for a small fee.
Mostly we just let the dogs play and we talk about Yorkies of course. I've tried different things though, like organizing groups for benefit walks (we have group T-shirts and doggie bandanas), BBQs and potlucks, and holiday parties. The Halloween costume party usually sees the biggest turnout of the year. We have over 100 members but usually have 20-35 dogs at events. I've also sponsored an intro to agility class, puppy obedience class and a pet first aid class (without dogs). I have some Yorkie-sized agility equipment I set up when we use the school yard. And currently I'm planning some obedience type games.
I do find that at the meetups I spend very little time getting to know "people" because it's so busy with dogs (I'm working on that). And most of us know the Yorkie names better than the owners. We are always welcoming new members!