Change url when manually scrolled to an anchor?

Try using this jquery plugin: Scrollorama. It has tons of cool features and you can use window.location.hash to update your browsers hash.

Alternatively, you can add a “scroll” event to check when an anchor is reached.

Here is a working fiddle to illustrate the event: http://jsfiddle.net/gugahoi/2ZjWP/8/
Example:

$(function () {
    var currentHash = "#initial_hash"
    $(document).scroll(function () {
        $('.anchor_tags').each(function () {
            var top = window.pageYOffset;
            var distance = top - $(this).offset().top;
            var hash = $(this).attr('href');
            // 30 is an arbitrary padding choice, 
            // if you want a precise check then use distance===0
            if (distance < 30 && distance > -30 && currentHash != hash) {
                window.location.hash = (hash);
                currentHash = hash;
            }
        });
    });
});