First, if you don't already know about them, I would recommend both the
WiiBrew Wiki and
GBAtemp to keep up-to-date with new releases.
Also, I'd recommend the
Homebrew Browser, which allows you to download from a repository straight onto your SD card through your Wii, so you don't need a computer.
And, you are eventually going to need something like
Wii Mod to load cIOS, WADs, etc.
As already mentioned,
WiiMC is awesome.
And of course, there are all the loaders: NeoGama, Mighty Loader, USBLoader, USBLoader GX, WiiFlow, uLoader, etc.
IIRC, only USBLoader GX and
WiiFlow have full NAND emulation, and
Mighty Loader is considered the easiest to use.
Also, I've been out of the scene for awhile, but if DIOS MIOS or DIOS MIOS Lite development ever continues, you may want to look into that (playing GameCube games off of either a USB external drive or SD card respectively).
Speaking of which:
It's a little out of date, but it should get you started.