If you want to do something in memory of Johnny Cash, you could do worse than re-read the lyrics to the song he sings on U2's Zooropa.

I'm proud to say that I worked with Johnny Cash, and when he came through the studio door for the first time it was like Moses himself had arrived. He is a character of truly biblical proportions, with a voice, all wailing freight trains and thundering prairies, like the landscape of his beloved America. Before I got to see it with my own eyes, I had a picture of it through Johnny Cash's singing. He has a soul as big as a continent, full of righteous anger mixed with human compassion. A true individual in a land founded on individuality. There will never be another like him, and he could have come from nowhere else.
--The Edge