There is the usual love-hate relationship with the Mac OS X Dock - some like it, others hate it. Those who criticize it often have not even used it, not even once. Personally, I find it useful but I always try to keep it a minimum since the ultra-fast Spotlight search tool often acts as my app launcher.

Anyway, Neil J. Patel has developed a "fully customisable dock-like window navigator for Gnome" and called it "Avant" (see image). This open source utility, whilst not entirely a Mac OS X Dock-replica, functions just like Mac OS X. I recommend checking out Neil's blog for screenshots and screencasts.

Who says Linux needs to be boring? :)