Experimenting with accessible forms, markup that's extensible for varied types of form layout, and with enough hooks to make validation simpler.

accessible-forms.haml

// options for :class to handle different form layouts
//		horizontal-labels - default
//		vertical-lables
//		overlay-labels

%form{:id => "", :name => "", :class => "", :action => "", :method => "post", "accept-charset" => "utf-8", "aria-role" => "form", "aria-live" => "polite", "aria-atomic" => "false"}

	%fieldset{:id => "", :class => ""}
		%legend
			%h3 Basic Input Fields
		%ol
			%li
				%label{:for => ""} 
					%span Basic Text Field
				.field.text
					%input{:type => "text", :id => "basic-text-field", :name => "basic-text-field", :size => "", :minlength => "", :maxlength => ""}

			%li.required
				%label{:for => ""}
					%span Required Field
				.field.text
					%input{:type => "text", :id => "", :name => "", :size => "", :minlength => "", :maxlength => "", "required" => "", "aria-required" => "true"}

			%li
				%label{:for => ""} 
					%span E-mail
				.field.email
					%input{:type => "email", :id => "", :name => "", :size => "", :minlength => "", :maxlength => ""}
					%span.guide email@example.com

			%li
				%label{:for => ""} 
					%span URL
				.field.url
					%input{:type => "url", :id => "", :name => "", :size => "", :minlength => "", :maxlength => ""}
					%span.guide http://www.example.com
			%li
				.fields.horizontal
					%label{:for => ""}
						%span Phone
					.field.phone
						%input{:type => "tel", :id => "", :name => "", :size => "", :minlength => "", :maxlength => ""}
						%span.guide xxx-xxx-xxxx
					%label{:for => ""} 
						%span Ext
					.field.text
						%input{:type => "number", :id => "", :name => "", :size => "", :minlength => "", :maxlength => ""}

Good suggestions. The HTML still seems heavier than I'd like it to be but it needs to be able to handle a variety of layouts. Reason for the .field class it that the form elements may not always be inside a list (for example if there's only one field element).

The lone legend wrapped in the fieldset was just a tabs/spaces nesting error. All fixed now.