This website held a lot of discussion boards on multiple topics on literacy and writing. However, I clicked on about four of those discussion boards and only one had comments. Maybe the website isn't that popular. It seems like a good idea though...I guess it could be helpful maybe it just need more publicity.
Tumblr is another blog space where you can create & post anything you'd like. There are topics is every area that you can search and find other blogs to follow that you have interest in.