There is this neat resource to help you plan for and discover (comics) conventions: conosaurus.

In their own words:

What is Conosaurus?

Conosaurus is a resource that helps independent creators and fans manage their convention schedules. We know there are quite a few convention databases already in existence, but we’re building Conosaurus to be as useful to exhibitors as possible. Most importantly, we’re keeping it free to use!

Currently, Conosaurus is focused on indie and mainstream comic conventions, zine fairs, and independent publishing festivals. We will expand to other convention types to meet the demand of the community. This is just the beginning!

Their website is getting a lot of traffic, so it glitches occasionally. seems to be stable as of right now. :)