milosevic - 1:55 am on May 28, 2012 (gmt 0)
I've done things like this several times.
Choose a CMS where you can import content from spreadsheets (e.g. Feeds module for Drupal).
Use a script to either extract content from the DB or scrape it from the site, whichever is easiest.
Format this for import (ie aggregate it into a .tsv spreadsheet)
Import the content into the new CMS.
I've also imported content manually via SQL statements (with an early version of Drupal 7) but it's a massive headache.