Hash read/write/delete functions
Streamlined code for get:

get: function(key){
    var lh = location.hash.replace(/^#/, "");
    var pairs = lh.split("&amp;");
    var obj = [], pair;

    for(var i = 0; i &lt; pairs.length; i++){
        pair = pairs[i].split("=");
        if (pair.length === 1) {
            pair.push(1);
        }
        obj[pair[0]] = pair[1];
    }
    return typeof key !== 'undefined' ? obj[key] : obj;
}, 


I also don't see why there's a callback passed to .set()?  There's no async operation and the callback is executed at the end of the function with no args so the caller could just put that same code right after the .set() call.  There doesn't seem to be any reason for a callback argument.