Thinking on a couple things
There are two ideas that have been buzzing around in my brain lately.
The first idea is a Perl CMS that is all Perl and that scales from CGI (because that is what a lot of cheaper hosting sites offer) to whatever you want to scale it up to. I don't mean scale in the traditional sense here, though I would want it to scale that way as well.
The second one is a server monitor along the lines of a Nagios but all in Perl with plugins written in Perl.
Neither of those is necessarily a "good" idea. They are just ideas. Throwing them up here to maybe tickle myself later with them.
I blog about Perl. I use Perl. I 
Munin has some similarity with Nagios.
Oh, there are lots of them out there. :-)
For the Perl CMS there is Movable Type, like this blog ;-)
What I need sometimes is a good local process and service monitor, that might also be controlled in a networked manner (e.g. decide if something should be restarted if it's ok on the other node). We are using mon for that mostly, but it's quite a resource hog, due to it's fork oriented design. I started playing with an AnyEvent based daemon, that would look for more suited to this. of course such a thing cuold be used like a munin node too, delivering performance data, but then again Munin is already out there.
MT is not all Perl unless the new version changed it. It uses PHP for some things.
Ugh, Nagios 3 now requires PHP. I hate it when people do that.