This is OK, but the better way to post to multipe blogs is to modify the content of each post so that the search engines see it as unique content. Also, for SEO purposes, your blog post should be a shortened version of a full article on your own website. Post your full article first on your website, then go ahead and post an edited version on a blog with a link back to your website. This is a great way to build both content and links to your site.