This may or may not be what you're asking, but I've found that if you have a form with
<%= text_field_tag 'foos[prop1]' %> <%= text_field_tag 'foos[prop2]' %>
<%= text_field_tag 'foos[prop1]' %> <%= text_field_tag 'foos[prop2]' %>
Then that gets handled by rails as {:foos => [{'prop1' => 'value 1', 'prop2' => 'value 2'}, {'prop1' => 'baz', 'prop2' => 'bar'}] }
Fred