I'd write that snippet the following way:

    for (var i = 0, ii = list.length; i < ii; i++) {
        sum += list[i].amount;
    }

Or:

    for (var i = 0, ii = list.length; i < ii; i++)
        sum += list[i].amount;

There are ways to make normal JavaScript not look ugly ;)

EDIT: fixed minor oversight