<p>Contact:<br/>
<table class="tbl">
  <% cells = 0 %>
  <% Contact.find(:all).each do |c| %>
    <% cells += 1 %>
    <% if cells.divmod(3)[1] == 1 -%><tr><% end -%>  
    <td><input type="radio" name="task[contact_id]" value="<%= c.id -%>" 
	<% if @task.contact == c -%> checked="checked" <% end -%> />
	<%= c.name %></td>
	<% if cells.divmod(3)[1] == 0 -%></tr><% end -%>
  <% end %>
</table>
</p>

radiobox collection in a 3 column table

table

Rails