Since I caught my shiny Elekid on the 5th of August 2008, I ain't had much luck getting more.
My shiny Geodude was in May 2007. Both were random. Man, that was over a YEAR before a second shiny came to me! :(
I tried chaining Swablu and Ponyta outside Celestic City, but that didn't work. Then I went down to the grass outside Jubilife to chain Bidoof, Starly and Ralts, but EVERY CHAIN I TRIED fizzled out at about 6 or 7.