A couple of years ago I started building feed aggregation sites (aka "planets") using Plagger. Once you've installed Plagger, it's pretty simple to configure new planets.
Notice I say "once you've installed Plagger". Plagger is one of those CPAN modules which installs about half of CPAN. The CPAN dependencies page currently gives you a 26% chance of successfully installing Plagger.
The reason for that is clear. Plagger is an incredibly powerful tool. It is an all-purpose tool for slicing and dicing web feeds. It also includes special-case plugins for creating web feeds for many sources that don't currently publish them.
So the net result is that Plagger is large and often hard to install. And most people (or, at least, I) don't use a fraction of its power. I wish I didn't have to install all of Plagger's dependencies in order to just grab a few feeds and combine them into a planet site. Perhaps the Plagger team needs to look at breaking up the distribution into smaller parts that do less.
[Update: Miyagawa points out that the vast majority of Plagger's dependencies are optional, so I'm overstating the case here. Sorry about that.]
Recently I moved a lot of my sites to a new server. And I really didn't want to go through the pain of installing Plagger. Therefore all of my planets have been dead for a couple of months. And that has been bothering me. But a couple of days ago (prompted by something that Paul Mison wrote) I decided to do something about it.
I a few hours of spare time I wrote Perlanet. It doesn't do anything at all complex. It reads data from a YAML file, uses XML::Feed to parse the feeds and then the Template Toolkit to generate the web page (oh, and XML::Feed again to generate the combined feed).
It's very simple. And it's new, so there may well be bugs. But it's there if you find it useful. It's already powering a revived planet davorg. My other planets should come back to life over the next few days.
I'm sure I'll be adding more features over the coming weeks, but the main point is to keep it simple.
 After Planet the Python software that (as far as I know) first popularised this method of aggregating data.
 Yes, I know it's a terrible name. But it seemed obvious to me and now I can't shake it.