This is actually quite old. But seems many people still don't know about this exploit, so I thought i'd share the method I use. It's a good alternative to Smash Stack. Team Twiiizers released Letter Bomb some time ago. Basically it saves a hacked letter to your SD card that when opened, will load custom code, (I.E. Gecko, PM Launcher, HB Installer, etc.)
A link to the wiki:
http://www.wiibrew.org/wiki/LetterBombVideo tutorial of it in action:
https://www.youtube.com/watch?v=ItsaNNT7RcIIt has its pro's and cons.
PROs:
1) It does not have the 2 gig SD card limit, this means you can load much larger mods Such as Legacy XP hackless.
2) It's quite simple to set up from the website, where you just enter your Wii's mac address to sign the letter.
3) You do not need to delete all your custom stages in the game.
4) It's available in all regions.
5) It does not require a particular game to function.
CONs:
1) It will save the letter to a specific day on the SD card, and it may be annoying to backtrack and look for it over and over, especially as time passes.
2) It will only work on the Wii that you entered the mac address for. You will need to repeat it for each console you wish to use it on.
3) It only works on menu 4.3+.
4) New things are scary to most people.
5)
This does not work on the Wii U.