Dop-IOS lets you download and install any IOS from Nintendo servers. You can also apply the trucha bug to them.

Features:

Download any IOS from Nintendo servers
Select between oldest version or newest version of any IOS
You can apply the signature hash check (trucha) again
You can also apply ES_Identify function patch to IOS36 (useful for AnyTitle Deleter and >3.4 users)
Protection: you cannot install stubs. You could get a brick if you install an stub IOS that your System Menu uses. If you want them, just update through Wii menu or disc.
Stores files on SD: you can reuse all your downloaded IOS with Dop-IOS or another application.
Shows your IOS versions

Changes:

Updated to all 4.2 new IOS.
Gamecube pad support.

http://wiibrew.org/wiki/Dop-IOS