NUS Downloader, or NUSD, is a PC Utility designed to allow easy access to the resources present on Nintendo’s Update Servers. Using this tool, you can download, pack, and decrypt many system titles into WADs ready to install.

Changes:

Directories are created with the version number when known (ex: 0000000100000002v289)
Certificates (cert.sys) no longer hard coded. You will be asked to generated the file on first boot of v1.1. This is done right from NUS.
Ability to alter the name of the packed WAD from the GUI.
Loading a TMD for info displays more information, such as what IOS a title requires.
Textbox output is a bit cleaner.
You can now choose to continue the download if a ticket (cetk) 404s. This will allow you to download the content of the titles, however you will not be able to pack them.
Decryption of contents now included. Needs common key (key.bin) to work! (Pro Note: DSi decryption will work with a (dskey.bin), however that doesn’t exist now)

http://wiibrew.org/wiki/NUS_Downloader