The best replacement for flock is firefox.

The best alternatives to flock are rated as following:
★★★★★  firefox
★★★  herd
★★  herd of sheep
★★  rockmelt
★★  internet explorer
★  fcntl
★  gaggle
★  mecha flock
  static grass
  lockf
  covey
  sticky flock
  cair
  fold
  3c
  camino
  lockfile

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

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



Google Trends

Scale is based on the average worldwide traffic of flock in all years. Click on graph for more.
flock
firefox
herd