Using form_for multi-select fields with acts_as_taggable_on
There needs to be two pairs of brackets, one for the options, and one for html_options, like so:
<%= f.select :skills_list, options_for_select(["Asst", "dir", "pres"]), {}, {:multiple => true, :class => "chzn-select", :style => "width:450px;" } %>