I have made an effort recently to posts more often - I think 2-3 times a week is about right for my type of blog which is mostly for keeping members updated about the website or about useful information I think will help them grow their business.
Committed bloggers should try to post once a day. If you perhaps don't feel like writing a big opinionated or analytical post, try posting a few short factual snippets. But I do try to make one big post a week, the purist that I am !