There’s a compilation called “Cani Arrabbiati”, where there are many great new bands that cover spaghetti western themes, and other Italian film scores from horror, giallo and euro crime movies. I think it’s on Spotify. There’s a pretty good “Great Silence” cover there by Anima Morte. But I don’t know of any surf bands or such, that make their on music in the spaghetti western style.
There are always examples of known artists that sample spaghetti western scores. Prodigy made a song where they sample a few seconds of Morricone’s score for “The Big Gundown”. The song was simply called “The Big Gun Down”: http://www.youtube.com/watch?v=kPD-_Q0c5XA
Gnarls Barkley also made a hit called “Crazy”, that sample the score for “Viva Django”. I just discovered this recently. But seems like it’s a really big hit. It has almost 7 million views on YouTube! http://www.youtube.com/watch?v=Qe500eIK1oA