The best replacement for github is bitbucket.

The best alternatives to github are rated as following:
★★★★★  bitbucket
★★★★  google code
★★★  sourceforge
★★★  svn
★★★  git
★★  gitlab
★★  beanstalk
★★  stash
★  sourcetree
★  tfs
★  subversion
★  gitorious
★  codeplex
★  github enterprise
★  jira
★  perforce
  mercurial
  unfuddle
  visual studio online
  gerrit
  trac
  tortoisesvn
  launchpad

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

Other search terms related to github and their ratings are:
★★★★★ eclipse
★★★★★ xcode
★★★★★ visual studio
★★★★ visual studio 2013
★★★ netbeans
★★★ jira
★★★ unity
★★ svn
★★ jenkins
★★ git
★ basecamp
★ intellij
★ bitbucket
sourcetree
tortoisesvn
You have in mind a companion for github and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of github in all years. Click on graph for more.
github
bitbucket
google code