Microsoft get a lot of stick for developing and delivering monstrous bloat-ware rather than lean and mean functional software that just does the job. Occasionally though, they really get the balance right and Windows Live Writer is one of those. It's a free (as in beer) lightweight offline blog post editor.
If you don't post articles to blogs often then you may be forgiven for assuming that blog sites must surely support some pretty advanced (i.e. intuitive, easy to use and reliable) post editing features. I don't have much experience in this field but I can tell you that the post editor in Blogger at least is abysmal. Blogger's online editor is only partially WYSIWYG, breaks many of the common user interface conventions and has failed more than enough times for me to get labelled unreliable. Windows Live Writer by contrast is a lightweight and (so far) perfectly reliable offline editor. It integrates incredibly well with a range of Blog sites, including Blogger, and my initial impression is that it is easy to use, accurate and reliable.
It detects your blog's layout and style template(s) and applies them on the fly so you actually get WYSIWYG editing. It allows you to easily edit and republish posts after you realise that you just published complete rubbish and need to fix it. It allows you to manage posting to multiple blog hosts including Blogger, WordPress, Microsoft Live Spaces and more, easily and efficiently.
It appears to have the beginnings of a plug in developer culture kicking off so in addition to the basic Insert Hyperlink\Picture\Video\Table options you can add plugins to support proper Insert Code that preserves the structure of formatted code and Insert Code from Visual Studio that preserves syntax highlighted code. Now if only it supported Insert Code from UltraEdit\Eclipse I'd be away on a hack, but it's light years ahead of the basic options available directly from Blogger.
The only problem with it at the moment is that the main Windows Live Writer site appears to be unavailable at the moment which sort of takes the shine of this. Keep hacking away at it though, if you ever post blog articles then it's worth downloading and using.