Many children's literature authors have embraced the blogosphere, and they're gaining in numbers on Twitter. Here are the authors I currently follow on Twitter:
Mitali Perkins: @mitaliperkins
Sarah Dessen: @sarahdessen
Meg Cabot: @megcabot
Sharon Creech: @ciaobellacreech
Neil Gaiman: @neilhimself
This is an impressive list of YA authors on Twitter.
This long list of authors on Twitter includes children's literature authors.
And here is a great list of picture book authors on Twitter.
You don't have to post Twitter updates in order to follow authors. You just need to sign up for an account and find them online using the @ symbol and their Twitter name.
If you want to find non-children's literature Twitter accounts, try wefollow. I've found that to be one of the better Twitter directories.
I have to confess that I find blogs much more interesting than Twitter accounts. I particularly like Mitali Perkins's style of Twittering: lots of links to interesting articles, sites, etc, posts on children's/YA literature issues, and low on the "just had a chef's salad for lunch" type of Twittering (which I find boring, no matter who it is).