Well, I did it: I shoehorned feed aggregation support into an ikiwiki plugin. So now it can run as a cron job, pulling in updated from feeds, turning them into wiki pages, and saving the pages to disk, then rebuilding the wiki.
Turning a wiki that grew blog support into a Planet engine has some interesting consequences. One of which is that the aggregated posts can be edited in the wiki unless locked, but more interesting is that the posts are first-class wiki pages that can be linked to from elsewhere in the wiki, and that can stick around even after they've fallen off the Planet's front page (although I do need to code up the support for eventually expiring them).
Another interesting thing is how the feeds are configured: By directives embedded in the wiki pages themselves. So no need for config files, and the wiki page that configures the feeds builds into the web page that lists and shows the status of the feeds.
The nicest thing about it though, is how little code I had to write, and how targeted it was. 300 lines exactly for it all. No need to deal with RSS generation, page formatting, full text search, any of that, it was all already there and works with the new source of pages like it would with any other pages.
Very happy with this. If you want to check it out, I've imported the data from Planet Debian upstream into updo.kitenet.net. Now if you find a new blog for a Debian upstream author, you can just edit the feeds page and add it yourself.
PS: No, I don't know why Jeff Waugh is flooding it, but it's probably a minor bug in the page creation date parsing. Too late to check. (Update: Bug in the atom parser, bug filed w/patch.)
PPS: I know about the problem with Lennart Poettering's blog encoding; a patch is in the BTS.