I just uploaded another script to my github repository.
It’s a python script to parse an opml file and generate a rss file with entries from all rss feeds in the rss file not older than a certain number of days.
You can get the script here: http://github.com/…/opml2rss.py
The script has a few configuration parameters that are pretty self explanatory, should be easy. You also need to install a few python modules: Feedparser, OPML and PYRSS2Gen.