router.js

// routes = [ [/test/, function(url){ console.log(url) }], ... ]

setInterval(function h(r){if(h.l!==(h.l=location.hash))for(r in routes)routes[r][0].test(h.l)&&routes[r][1](h.l)},10);

Depending on your browser or environment you can also use window.onhashchange (if this is for Zepto and you're only supporting Webkit and possibly other "modern" browser in the future, it'd SO work). However, it's 4 bytes more than danilocelic's answer.

addEventListener('hashchange',function(h,k,r){h=location.hash;r=routes;for(k in r)r[k][0].test(h)&&r[k][1](h)});

Well, if you don't care about overwriting events, you could drop the addEventListener entirely and, as long as the code runs in the DOMWindow context, bind directly to onhashchange. You could also save 5 more bytes by letting h, k and r leak into the global scope.

Also, the semicolon is pretty pointless...

this.onhashchange=function(h,k,r){h=location.hash;r=routes;for(k in r)r[k][0].test(h)&&r[k][1](h)}

^^ Yeah, but that's gross, :P