Blogging is a type of journaling, so if you're reading this, you're probably on the right track. :D If you get stuck for ideas, consider blog prompt lists or journal prompt lists.
I never realize how much I've accomplished until I pile it together trying to catch someone up on what I've been doing. So that's one way blogging is useful to me. I can use posts to track things over time, like my goals for the year. I also have regular posts, like the Monday Updates, and various lists to encourage discussion, like the self-awareness questions.