The blog software I use is MarsEdit by Red Sweater. I find this to be really excellent. You can use it without any knowledge of HTML or CSS but a bit of knowledge opens up many possibilities with MarsEdit.
As a default MarsEdit will allow you to position an image left, middle or right using the old fashioned “align” tag which works fine but isn’t a “float” of course.
I do float images left and right myself but I keep some boilerplate HTML/CSS for doing this and it works well.
I use MarsEdit with Wordpress blogging software on my server and they work very well together.
I highly recommend Google’s Blogger: blogger.com
It’s free and you write/edit entries via Safari or any other browser.
No knowledge of html is required, but it’s helpful if you know it.
Placement of pictures is easy, and yes, you may float them left, right, or center.
You may also write RTF in either Scrivener or TextEdit and copy/paste it in.
You could try MacJournal, which will do stand-alone as well as posting to a blog.
Journler is another alternative but to blog with this you need to use MarsEdit (or similar) as an intermediate step. With Journler ‘post to blog’ simply opens MarsEdit and copies the entry when you can make any HTML alterations and then post to your Blog. Journler is not intended to be used as ‘pure’ Blog software, hence the kludge. I think this combination, with the ability to add HTML tags in MarsEdit would do what you want. Keep the post in Journler and then submit to Blog when a connection is available.
And, if you don’t mind dealing with the evil empire, Microsoft Live works as a cloud based app. (But why bother? For example, the free, and unequaled, wordpressdotcom allows web-based input fine. Why go to Microsoft Live to do the same thing. But, some folks do. No accounting for taste?)
I have started to use Scrivener to write my blog texts. I use Flickr to show images in my blog, so it makes no difference for me if I write my blogtexts directly in Mail application or first in the Scrivener and then copy-paste it to the Mail. I use Posterous, so I just use Mail to send my blogtexts.
The reason why I have started to write my blogtexts in the scrivener is simple: If Posterous quits its service, I have my blogtexts on my hard drive too. Also, it is much easier to search stuff from my blog if texts are found on Scrivener. Scrivener also have Full Screen Mode which I love. Great app, have to say.
I have used Scrivener for this, but placing images is a bit of a pain depending on the length of the piece.
MarsEdit is one on my to try list (others in this thread mentioned)
I tried one called “Blogo” a while back and recall liking it, plan on testing it again. As those apps both I believe integrate straight into wordpress (which I use on multiple sites) it works a bit better than scrivener for me… though I still have a .scriv project for each site that I use for drafts and brainstorming.