If you are looking for some constructive feedback on your writing I recommend Writer's Cafe. It is an online community for writers that works the same way as say, a writing group meeting at a cafe. If you want to publish online, enter contests, join writing groups, and meet other writers- most who give useful feedback, then this is your place. It is also possible to advertise your work for a fee. Let me know what you think of this new online writing community. And for those of you who are really serious about getting feedback from other writers, check out Scribophile. On there you will see a lot of works in progress such as chapter books and collections. Happy Writing!
