This is my promised list, based on newsletters I receive and find useful. All of these are free, but you need to be aware that what that sometimes means is there is a bigger, more informative version that you have to pay for. The best way to assess these is to ask for a sample first. Most newsletter people are happy to provide you with one. These are the ones I know of - if any of you have others that you would recommend, please do provide details in the comments.
Publisher's Weekly has a number of free newsletters. I subscribe to the Children's Bookshelf which is the newsletter aimed at children's writers (or anyone interested in children's books). If you go to this link here, you will see a whole pile of their newsletters and you pick which ones you're interested in. Choose wisely. Somehow I ended up on their cookbooks list and no matter how many times I've tried to unsub, it ignores me!
Randy Ingermanson is known as the Snowflake Guy, because he wrote this article about how to plot your novel using a snowflake kind of plan. If you go to his website, you'll see plenty of things of interest to fiction writers. Randy's fiction writers' newsletter is free, and often includes handy marketing advice. He also has free articles on his site, as well as stuff you have to pay for. I use his article on scene structure in my classes. Look around and see what you can use.
Margie Lawson and Mary Buckham produce a monthly newsletter - if you've done one of Margie's courses, you'll find the character analysis materials useful. There are other snippets and interviews of interest - this one may only suit some people. You can sign up on Margie's site - scroll down to the bottom of the homepage.
Anastasia Suen has a few blogs, but one which has morphed into a group that sends email updates is her Chidlren's Book Biz News. Google her for the range of blogs and news updates she offers.
Publisher's Marketplace has an extensive newsletter as well as a site where you can check out publishers, agents, new book deals, etc. But for those of us on a budget, you can subscribe to Publisher's Lunch - the light version. Their Friday Deal Lunch is a real lesson in how to sum up your book concept in one or two sentences and make it sound like a zinger!
Write4kids is an extensive website with dozens of resources such as articles and a writer's clubhouse. They have a newsletter that you have to pay for, but the "light" version usually has one good article in it, as well as lots of links and special offers. I'll talk about the newsletter when I get to the Newsletters You Pay For post.
Moving on from writing to life in general, I get Craig Harper's blog posts via email 3-4 times a week. If you want a real good kick up the rear end about all kinds of things, you can subscribe to this one. Be warned - Craig is not about making you feel warm and fuzzy. Subscribe here or go to his site and scroll down to the bottom of the last post in the middle. Note to Craig - you need to tidy up the site, mate.
Now, the business newsletter I subscribe to comes from Nightingale-Conant. I found them through their online tool that helps you define your mission statement. If you've never thought about doing that as an author, you might find it interesting. The NC newsletters are very often aimed at business people, sometimes the focus is goal-setting or motivation, but I still find stuff in there that's useful to me. A recent article was about why you should look at ways to reinvest in your core business (which for me is writing) rather than pull your belt in and cut off the circulation. This one is up to you - you might find it useful, or might think it's totally irrelevant! I get the AdvantEdge newsletter and the daily quote (sometimes they are real humdingers!).
If you belong to an organisation, such as the SCBWI or the Australian Society of Authors or any of those kinds of things, you will receive a newsletter as part of the deal. This doesn't mean they're free, but you don't have to pay extra. Sometimes, the quality of the newsletter might be the 'make or break' element that helps you decide whether to keep on as a member.
These are the ones I subscribe to currently. They change. Sometimes I realise that I'm not reading a certain newsletter and it's just clogging up my email so I unsubscribe. If you have a great free newsletter for writers that you'd recommend, please let us know.