I've had quite bad luck lately with the Blooger BlogThis! bookmarklet. It simply fails to open much of the time with both Firefox and Camino. On the other hand the Google toolbar for Firefox "Send To Blogger" function has been working quite well, and of course on the XP platform there's Microsoft's unrivalled "Live Writer" for both IE and Firefox.
Alas, Camino and Safari are left out in the cold, though the BlogThis! bookmarklet seems to work best when I try it with Camino.
Send To Blogger is no panacea though. There's still no category/tag support.