[Aetae]

На ваш вкус.)

function searchBetween(str, first, second){
    var fl = first.length,
        sl = second.length,
        f, s = -sl,
        arr =[];
    while((f = str.indexOf(first, s+sl)) !== -1 && (s = str.indexOf(second,f+fl)) !== -1  ){
        arr.push(str.slice(f+fl, s))
    }
    return arr
}

function searchBetweenReg(str, first, second){
    function escape(str) {
        return str.replace(/[\-\[\]\/\{\}\(\)\*\+\?\.\\\^\$\|]/g, "\\$&");
    }
    var result = [],
        arr = str.split(new RegExp(escape(first) + '([\\s\\S]*?)' + escape(second),''));
    for(var i=1, l = arr.length; i<l; i+=2 ) result.push(arr[i]);
    return result
}

function searchBetweenReg2(str, first, second){
    function escape(str) {
        return str.replace(/[\-\[\]\/\{\}\(\)\*\+\?\.\\\^\$\|]/g, "\\$&");
    }
    var reg = new RegExp( escape(first) + '([\\s\\S]*?)' + escape(second),'g'),
        arr = [],
        sub;
    while((sub = reg.exec(str)) !== null) arr.push(sub[1]);
    return arr
}