One reason to stick with Gentoo Linux is the superior portage package mangement based on BSD ports and the thousands of packages (i believe more than 15000! nowdays) to choose from.
Nevertheless, some packages may exist that have not yet make it to the official portage tree. Although one could use the corresponding ebuild, outside the portage tree, in a local overlay, nowdays there is the possibilty to add a bunch of such overlays by using the layman utility, e.g. “layman -a voip” will add the voip overlay, containing voip related ebuilds to a local portage tree.
I found out about layman while searching for a SMplayer ebuild which is located in the berkano overlay along with other interesting software. Other “extra” packages found in overlays include the azureus-gcj build, second-life, NX server and many more.