The best replacement for usenet is giganews.

The best alternatives to usenet are rated as following:
★★★★★  giganews
★★★★  p2p
★★★★  bittorrent
★★★★  usenext
★★★  torrent
★★★  newsgroups
★★★  irc
★★  seedbox
★★  private tracker
★  astraweb
★  torrents
★  newshosting
★  rapidshare
★  btguard
★  google groups
★  listserv
  easynews
  freenet
  newsgroup

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

Other search terms related to usenet and their ratings are:
★★★★★ sickbeard
★★★★ usenext
★★★★ tor
★★★ nzb
sabnzbd
isp
You have in mind a companion for usenet and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of usenet in all years. Click on graph for more.
usenet
giganews
p2p