I have chums who write several blogs, amongst which would be say a family related one, a subject specific blog and a work focussed one. However, running these can be incredibly cumbersome if you have to log in and out different services/accounts. Moreover, if one post is to be used on several of the blog eg intersection of subject and work blog, then it is a case of cut and paste.
However, a much better approach is to use a service like WriteToMyBlog which was created by Mark Ascroft. It allows a single post to be submitted to one or more blogs simultaneously. Very feature rich, it has great wysiwyg post writing/editing facilities that are much better than many mainstream services eg insert and manage tables. You can also handcraft your post in html if you wish.
The service is free to use and doesn't insist on any sign-up, albeit it's convenient for regular users to do so as it will save the details of all of your blog account, thereby having to enter them each time.
I got to know Mark last year as we are both cricket fans and chatted via skype about the England v Australia games during the matches – he is an Australian living in Australia. He created the service in his spare time and did an excellent job in my view.
Even if you only have one blog you maintain, give it a try and let me know what you think.