Sending the selected option of a select via ajax

Hi,

i want to create a form which contains 3 select-boxes which content
depend on each other.
i created the first select box:


<% for project in @projects %>

<%=project.name-%>

<% end %>

the :id => ??? should be replaced with the id of the project in the
selected option-tag, but… how?

greetings,

Pascal