The best replacement for kazaa is limewire.

The best alternatives to kazaa are rated as following:
★★★★★  limewire
★★★  morpheus
★★★  bearshare
★★  napster
★★  kazaa lite
★★  frostwire
★★  emule
★  ares
★  winmx
★  imesh
  shareaza
  gnutella
  riaa
  edonkey
  lime wire

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

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



Google Trends

Scale is based on the average worldwide traffic of kazaa in all years. Click on graph for more.
kazaa
limewire
morpheus