I follow a lot of Twitter users among my accounts; probably somewhere around 400-500 different twitter-ers. Because of this, I often get some awesome links to tutorials, guides, how-tos, and general information; many links which I would miss otherwise, because they won't show up on reddit, digg, or other social link sites.
When Twitter users give high-quality, low-visibility links, users read their tweets and blogs more often than the users who spam their Twitter streams with tons of links to their own content. In my opinion, very few people can often and consistently write top-notch content on their own blogs. There are exceptions, but most bloggers are not professional writers, and therefore need to focus not solely on their own writings, but on others' as well.
For both my geerlingguy and MidwesternMac Twitter accounts, I usually just give one link to a new posting from my sites that I think might be interesting, whereas I might re-tweet or aggregate links to many other people's sites throughout the course of the week. Why? Because I think that will be more helpful to the people following my Twitter stream. And that, along with my ability to communicate with them via Twitter, is what will keep them following me.