Rails form tag and options helper for easily constructing jQuery driven
drop-down menus. 

http://www.filamentgroup.com/lab/jquery_ipod_style_and_flyout_menus/

Copy the jquery_dropdown_helper.rb file to <your-rails-app>/lib 
Use the tags or helpers in your views. 

Examples: 
# <%= hidden_field_tag sort_criteria %>
# <%= dropdown_tags sort_criteria, 'Select Criteria', 
# 	%w(Category Status Amount-High Amount-Low) %>
# # => Creates a drop-down with four items. No callback specified

# <%= hidden_field_tag 'budget_main', @budgets.first.id %>
# <%= dropdown_tags 'budget_main', @budgets.first.name, 
#	@budgets.map {|x| [x.name, x.id]}, :select => 'onBudgetSelect' %>
# # => A drop down menu comprising of budget items, showing name of 
# # first budget item, with resultant javascript callback 
# # onBudgetSelect(selected_value) when a menu item is selected.