The tag thing was a bug that I've fixed - it no longer shows tags from deleted/unpublished entries in the 'tag cloud'.

Currently I'm afraid there's no way to add content to pages controlled by applications (unless the application itself allows you to). I could look into adding this if it's something more people would like to see!

There's also the option of creating a blog-like section using CMS pages and Filtered Item List, like this. The advantage is that you can put content wherever you like, but you don't get a calendar/archive as you do in the weblog app.