For the mac users there's blogo. By the time of this writing, the version 1 has been discontinued and the version 2 hasn't yet been released, but there's a video on the official site showing its capabilities. Those include:


WordPress, tumblr and blogger / blogspot support
Offline composing
Editing of already published posts
Visual editor that uses the actual site theme to render the preview


Possible drawbacks:


Works only on mac
Not free


Looks like it doesn't offer spell-checking natively, but there will be a plugin system and it's possible that there'll be a speelcheck plugin for blogo:


  Power Ups are add-ons that will be available via in-app purchase to make your Blogo experience even better. 


Offline WordPress post editor/creator
We have a Web KB that is built in PHP.  Is it possible to setup a web tab in Salesforce which will go to this KB without needing to login using username and password?

I initially thought that SAML may help and that I can use salesforce as identity provider.  However,  the Service Provider PHPKB does not support SAML.

I am thinking of getting session ID from salesforce and pass it to KB for autohentincation.

However, I don't know how to do it. just a theory
