#BookMarketingChat is held (every Wednesday evening at 9pm eastern) . It was created about four years ago to help writers learn how to market their books. It covers all manner of topics: social media, book marketing, book promotion, branding, publishing, and writing. There are expert interviewed most weeks.
#WriteStuff is held every Tuesday at 9pm eastern. Topics vary, but it's mostly writers talk about writing. It's not genre specific and publishing experience isn't necessary. It gives writers a chance to commiserate with and learn from each other.
#WriteChat is held on Wednesdays at 8pm eastern. Each chat consists of three writing prompts slash questions that share a single theme. The questions relate to your writing style, WIP, main characters, and even the writer. All writers welcome & can answer questions anytime.
#WordMagicChat is held Tuesday evenings at 7:30 pm eastern. It is less a chat than a collective writing sprint.
#IndieAuthorChat is held on Wednesdays at 3pm eastern. It is organized by Alliance of Independent Authors, and usually consists of an expert interview, although of course everyone is invited to answer the questions based on their own experiences.
#WritersLifeChat is also held at 8pm eastern on Wednesday. I don't know much about it.
#StoryDam is held at 8pm eastern on Thrusdays. It's not clear how it is organized, but I did see the host answering questions.
#StorySocial and #PubChat are held at 9pm eastern on Wednesday. I don't know much about them.