Params from a collection_select

no idea what you want .... i#ll just give an example:

<%= collection_select :post, :category, @categories, :id, :name,
{:include_blank => true } %>

will generate

<select name="post[category]">
<option><option>
<option value="1">Diary<option>
<option value="2">Technical<option>
<option value="3">Rants<option>
</select>

- object + method form the name="post[category]"
- the collection has the input for the option tags.
- value_method is the method to use on the collection items to get the
value for value=""
    here: @categories.id
- text_method is the method to use on the collection items to get the
display text for the options
   here: @categories.name

- the options hash take the options as explained in the API docs of
FormOptionsHelpers, e.g. the :include_blank i used above to create an
empty <option> tag
- the html options hash takes the usua stuff like :class => "something"
etc....

when the form is submitted, you can access the selected value with
params[:post][:category]