there's a homebrew USB loader for the Wii that requires no extra hardware (other than a USB HDD and an SD card). it doesn't work for gamecube games, though.
Games are not 7gb+, only a handful are on dual layer DVDs. And Luke is right, when you convert the game to .wbfs to put it on your HDD, it becomes drastically smaller. Most games are 2-3gb, and some are less than a gb.
Anyway, personally I prefer Configurable USB Loader, and I use that along with CRAP to put channels for some of my favorite games straight onto the Wii menu.