Spotify open works (well... more or less, though you cannot add your own music collection to it) under Wine (
www.winehq.org). There are a bunch of other services like Spotify. For example grooveshark (
www.grooveshark.com), rara (
www.rara.com) and sony music unlimited (
www.sonyentertainmentnetwork.com). Of those grooveshark is the only free one (actually it's ad-funded). They all work in browser, so no software installation is required to use them. One possibility is to just use youtube as your music source, though in that case you might not find sound quality acceptable in many cases. There is a simple interface for listening music from youtube called youtify (
www.youtify.com).
