One of the reasons I like posterous (other than its awesome multimedia media support) is that when I create post their I can set it up to tweet to my twitter account about my latest post.
WordPress.com is still my first love when it comes to blogging so I thought there has to be a way to tweet about my new post and I finally found it after a lot of googling. So it is a bit obscure.
* Login to wordpress.com
* Go to your blog’s dashboard by clicking “My Dashboard”
* Click on “My Blogs” under Dashboard
* In front of the blog name you want this for (in case you have multiple blogs like me) look for the “publicize” column and check Twitter. WordPress uses oAuth to authorize (did not ask me my twitter login)
* Post new blog entries on WordPress.
PS: Did not find this (http://en.support.wordpress.com/publicize/) when googling but when I searched for wordpress.com publicize.