Hey Kenny,
Here's an aspect of cells that I haven't seen highlighted before.
The html macros I made pretty much constitute a schema for html. Not only does it concisely say what attributes are allowed on each element, but it gives you the object model for dealing with instances of these elements, and a nice set of macros for easily creating them.
A couple of "validation" defmethods and I think we've got something that may be better even than relax-ng (the unstated assumption here is that its not hard to be better than xml schema).
I know that lispers generally aren't that fond of xml but I bet there are a few that use it on their day job (as someone who's day job involves dealing with CDISC's various models it certainly is important for me).
Since you're using your blog as a lisp/cells advocacy platform, maybe you could demonstrate this by creating a few macros that do a similar thing for RSS. I'd do it myself but I don't have a blog (I've never really felt that I've had enough to say to merit it but I am starting to get itchy fingers these days, hence the ramblings on cells-devel).
-- Andy