Sabayon
If you use Firefox (on Windows, Mac, or Unix)...
the easiest way to download with Metalink is DownThemAll! (Cross Platform Firefox Extension, Open Source). Just install DTA, then right click the Metalink for the flavor of sabayon you want, and select "Start link with OneClick!"
You can also install a download manager, Free Download Manager (Open Source), wxDownload Fast (Open Source), GetRight, Net Transport, Orbit Downloader, and Retriever work well. (These integrate with Firefox with the FlashGot extension).
You could also install another web browser, TheWorld Browser.
There's also a Windows version of aria2 and Metalink Checker, both excellent command line downloaders, but they may only be appropriate for those comfortable using non-graphical applications.
GGet (GTK) is a great download manager for GNOME. There's KGet2 in KDE4.
aria2 binary packages are available for many other distributions. There's also Retriever and wxDownload Fast, download managers that can be integrated with Firefox with the FlashGot extension. Metalink Checker is another excellent command line downloader.
Speed Download (Mac) is a slick Download Manager with fast downloads & P2P filesharing. It integrates with popular Mac browsers like Safari, Camino, & Firefox (along with 5 others). Retriever also works on Mac, along with aria2 and Metalink Checker for command line users.
Metalink is also used by OpenOffice.org, cURL, openSUSE, LugRadio, DOFUS, UniProt Consortium, Eiffel Software, 64 Studio, ADIOS, Arch Linux, Bayanihan Linux, BeleniX (OpenSolaris), Berry Linux, blag linux, Bluewhite64 Linux, DesktopBSD, GoboLinux, Granular Linux, KateOS, Linux Mint, MidnightBSD, Pardus Linux, PC-BSD, PCLinuxOS, PuppyLinux, redWall Firewall, StartCom Linux, TrueBSD, Ubuntu Ubuntu Christian Edition.
* Automatic error correction is supported by Retriever, aria2 and Metalink Checker. If you start your download with another program, and get errors, aria2 can resume & repair the error as well.