Is there a good place to find upcoming LEGO conventions? Is there a continually-updated site that tracks LEGO conventions/gatherings around the country (USA) or world? Ideally there'd be a way to filter them by date/type/location.
There is the LEGO ambassadors network calendar:

https://lan.lego.com/calendar

This contains all events organized by RLUGS (LEGO communities recognized by LEGO), which are the largest events generally.

However, where I live, all sorts of communities and individuals organize events, it is quite a challenge to keep track of all of them.