I have been using Snipsly and Jevitt recently. I think it's worth getting into the habit of using them to regularly promote blog posts and articles.
Of course it's worthwhile having your links seen by others on these bookmarking sites as well as getting the SEO boost they can confer, but these aren't the only benefits.
For each link you add you have to write a new little summary of what you're linking to, or at least some mini-article that's related to it somehow. Of course you don't want to waffle on with these summaries. You should get right to the point with a pithy and accurate summary. And, each of them has to be unique. So, every one presents a little writing challenge. Doing this regularly can increase your writing speed and quality.