The best replacement for subdomains is subdirectories.

The best alternatives to subdomains are rated as following:
★★★★★  subdirectories
★★★  subfolders
★★★  folders
★★  directories
★★  domains
★  addon domains
★  separate domains
★  microsites
  multiple domains

Your alternative for subdomains is not listed? Suggest!
Speaking about subdomains, one probably shouldn't forget about google analytics.

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



Google Trends

Scale is based on the average worldwide traffic of subdomains in all years. Click on graph for more.
subdomains
subdirectories
subfolders