I like to play last.fm streams in Amarok, rather than the last.fm player. I also sometimes browse the last.fm website (using Konqueror) and I would like the 'Play in software' links to use Amarok instead of the last.fm client. To do this, save this file as $HOME/.kde/share/services/lastfm.protocol. Contents below in case the download won't work:

[Protocol]
exec=/usr/bin/amarok "%u"
protocol=lastfm
input=none
output=none
helper=true
listing=
reading=false
writing=false
makedir=false
deleting=false