24 Channel voltage sensor using Arduino

I am an absolute novice. I've always been more of a software guy, but lately I've been trying to play with more hardware.

I need to build a 24 channel voltage sensor (0-5V). This is for a solar panel array project. There are 24 panels and I want to know monitor the input from each panel, from 0 to 5v. Would anyone here be kind enough to tell me what I need to make this happen?

This will be my first Arduino project.

Although it is a totally different project, this:-
http://www.thebox.myzen.co.uk/Hardware/MIDI_Footsteps.html
Is virtually what you need in terms of both hardware and software.