I have two blogs, and I hardly have times to manage them all. I'm trying so hard to be able to post a good content at least once a week for each blog, and usually I fail. How you do it? Writing a good content is more harder than I think.
Practice. I have one blog just for practice purposes. I write whatever emerges in my head. Write as fast as I can. Normally 10 minutes. If you want to make good content, you must already have the point. Gather information about the topic then start writing with your own word. When writing, write as fast as you can. Don't ever think about grammar or mistake. Writing is writing. Then only after you have finished the writing session, take a break and start editing. In this way, you can't stuck here and there. This is the way I write.
Webcrawler has good advice on writing. I update my blog every weekday. I think the subject has a lot to do with it as well. If its something you would be interested in yourself then it is easier to write about than something you have no interest in. They say, write what you know, but I also add, write what you like, because if you write about something you don't like or care about it will come out sounding just as meaningless as you feel about it. Our subconcious feelings actually DO come out in our writing, and the readers will pick that up.