I am currently searching for a way to import RSS from another blog (not running wordpress) periodically into a wordpress blog. the imported items (via RSS) should appear like normal posts.
i found a "wordpress-rss-import" plugin, which seems to to this task, but is quite old:
another variant would be the "wordpress-to-rss aggregator" from laughingmeme.org
- this seems to miss some features, like updated posts.