Once again, this isn't really directly an Emacs-specific thing, but it's something which Emacs users may find useful.

It's All Text is a plugin for Mozilla Firefox (but not yet SeaMonkey) which allows a user to edit HTML text editor boxes with the text editor of their choice. Thus making things like LiveJournal comment fields far less painful than they might otherwise be.

Personally I find it invaluable, especially when a comment thread starts getting on a bit (it's nice to be able to paste what I'm responding to into the scratch pad and just swap between buffers when checking details).

EDIT: If you install it, it's worth customising it and changing the order of file extensions to place ".html" before ".txt" so that C-x 8 character encoding is supported properly (for which you'll also want the language environment in Emacs to match that in Firefox; I use UTF-8). It shouldn't adversely affect text only boxes and doesn't require all HTML tags to be included in something like an LJ comment.