Although GenCon is primarily a celebration of table-top gaming (Dungeons & Dragons, board games, card games, etc.), it caters to writers as well, especially but not exclusively to those writing speculative fiction.
The group driving most of the writing seminars is the GenCon Writer's Symposium. As I post this, their site is not entirely up to date, and contains links to events from 2016. But it does have a lot of good info. You can find the complete up-to-date list of events on the GenCon site itself, and use their Event Finder. On the GenCon site you'll also find info on registration, badges, housing options, etc.
Some seminars are already sold out. But their are many, many left, on topics from world-building to inventing languages to writing action scenes to finding agents, and lots in between.
I'll be there all four days myself. I signed up for so many panels I didn't leave time for lunch or dinner one day.
Maybe I'll see you there?