var categoryLinks = {
    Foo: 'http://www.bing.com/search?q=foo',
    Bar: 'http://www.bing.com/search?q=foo+bar',
    Foobar: 'http://www.bing.com/serach?q=foobar'
};

Highcharts.chart('container', {

    title: {
        text: 'Click categories to search'
    },

    xAxis: {
        categories: ['Foo', 'Bar', 'Foobar'],

        labels: {
            formatter: function () {
                return '<a href="' + categoryLinks[this.value] + '">' +
                    this.value + '</a>';
            }
        }
    },

    series: [{
        data: [29.9, 71.5, 106.4]
    }]
});