We've noticed an increase in the number of splogs being created over in my neck of the woods on our elgg, drupal and wpmu installs. (I got yelled at. I have to bunch in our drupal installs when I say "elgg and wpmu installs" now.)
I know previously we've suggested going into the site admin -> blogs, sorting by Last Updated and doing right clicks -> Open in a new Tab and reviewing all of the blogs to see what they've done recently. This of course takes time and you may wind up with tens if not hundreds of open tabs which may all come crashing down on you.
We've been kicking around the idea of using Google's blog search engine and sorting by date. The difference with that is that you see a portion of the content via that method and then can choose if you want to do your right clicks to review the recent post. The problem with that is only the sites that have been made public and non-mature are seen. (Making a blog as mature is listed on a number of "How do I set up a wpmu splog?" lists I have come across. This is an attempt to keep the splog under the radar of the site admin.) Also not every blog is indexed by Google. This is a method I use to catch edublogs splogs.
We've also debated on updating itdanger's sitewide feed plugin, removing all of the public/ mature/ etc checks, and monitoring the complete feed off of that. The downside is that that plugin is notorious for it's load issues. Also while the plan had been to keep that feed a secret so that only the site admin(s) knows about it, if the url got out other folks would be accessing it and therefore causing more of a load.
Reporting slogs is a great method as well a way to encourage your endusers to participate in the maintenance of the site. You run into issues with ego though is there's a difference of opinion of what makes a splog and what doesn't. It's also very public which may or may not be a good thing for you.
What do other folks use as a method to nab sploggers?