The Qumana application is a flexible and easy-to-use tool for rapid assembly and publishing of microcontent to major blog hosts--Blogger, Blogware, TypePad. Our application allows you to easily gather and shape microcontent for your blog. It provides you with the tools to collect, combine, modify, package and publish microcontent that meets the information needs of your peers, clients, and business.
Note: I think this entry doesn't refer to the most current version. Make sure you get that from their website.
I evaluated this and passed on it in favor of Blogdesk (which is free and does everything this does -- at least, on Windows), but this would be a significant contender on Macs. It's cross-platform (Java), has a solid UI and some nice convenience features (like a "drop-pad" for posting from browsers), and seemed to perform well in my tests. Its HTML was reasonably clean and it worked with my (Drupal) MetaWeblog blogs.
You have to pay for it. As I said, if you're on Windows, check out Blogdesk. But the price is now reasonable. (Again, may not show accurately on this listing.)
Also, while it will upload embedded pictures, it won't upload linked PDFs or other binaries, and (at least in the version I tested) didn't have support for podcasts. (That last is probably not really their fault.)
Finally, while I didn't see this posing a problem in my tests, it was originally designed to integrate with an ad network. If I were to consider implementing it in an organization, I would examine its interactions for signs of active hooks back to the Qumana ad services. I recommend just asking them.