Here you can find converter RSS feeds to fb2 format.
It takes OPML or plain text file (with feed url at single line) as input data and returns fb2 book with structured tags/feeds/posts
This is simple python script. You can find it here:
feeds2fb2.zip
feeds2fb2.tar.gz
Some photos and usage samples you can find
here (sorry, description is in Russian)
bug reports and feature requests are welcome