blogg.de now also does tagging - and after I asked, now in the same way as Technorati. So with the category tag in the RSS feed if one is present there. Since I've always used categories like tags on my blog anyway, that's extremely practical - my posts end up in the right section on blogg.de. Nice. By the way, in my opinion that's also the smarter alternative to the easily set up group blogs as they should be implemented via Topicexchange - simply a central ping service and corresponding entries in the RSS feed.