Basic explanation of special relativity
It’s a bit dated, being from 2005, but this page from the University of New South Wales gives a very clear explanation of what special relativity is and how it has real-world applications.
Of course, because it’s from 2005, it doesn’t mention the apparently superluminal neutrinos reported by the OPERA experiment last year. I’ve said this before, and I’ll say it again: it’s most likely to be a very subtle error in the experimental set-up. The main reason I suspect that, along with almost every physicist in the world, is that the discrepancy reported was about 1 in 40000 – about 0.0025% faster than c – and it stayed constant regardless of the measured energy of the neutrinos, when there should have been a correlation between them.
Either way, enjoy the link.