The best replacement for twitter is facebook.

The best alternatives to twitter are rated as following:
★★★★★  facebook
★★  tumblr
★★  friendfeed
★★  identi.ca
★★  lichiko
★  instagram
★  rss
★  facebook users
★  texting
★  blog
★  myspace
★  facebook stock
★  tweeter
  plurk
  facebook more popular
  facebook which is better
  google plus
  facebook statistics
  whatsapp
  facebook advertising
  instagram users
  facebook yahoo answers
  twitter
  facebook status
  blogging
  linkedin
  google+
  reddit
  tweetdeck
  jaiku
  pownce
  weibo
  echofon
  text messaging
  facebook demographics
  tweetbot
  loopt
  facebook ipo
  ubertwitter
  tweet
  fb
  tweetie
  blogs

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

Other search terms related to twitter and their ratings are:
★★★★★ facebook
★★★ melissa
★★★ flickr
★★ most tweets
★★ signing in
★★ oauth
★★ instagram
★★ followers
★ facebook page
★ myspace
★ multiple accounts
★ hashtag
★ twitter
signing up
facebook account
comment
login
google plus
You have in mind a companion for twitter and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of twitter in all years. Click on graph for more.
twitter
facebook
tumblr