The best replacement for dotnetnuke is joomla.

The best alternatives to dotnetnuke are rated as following:
★★★★★  joomla
★★★★  drupal
★★★★  sharepoint
★★★★  wordpress
★★★  umbraco
★★  orchard
★  kentico
★  sitefinity
★  community server
★  rainbow
★  sitecore
  dnn
  mambo
  mojoportal
  liferay
  composite c1
  postnuke

Your alternative for dotnetnuke is not listed? Suggest!
Speaking about dotnetnuke, one probably shouldn't forget about webmatrix.

Other search terms related to dotnetnuke and their ratings are:
★★★★★ webmatrix
You have in mind a companion for dotnetnuke and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of dotnetnuke in all years. Click on graph for more.
dotnetnuke
joomla
drupal