diff --git a/actionpack/CHANGELOG b/actionpack/CHANGELOG
index 718376d14c7e8..6a38dd5b65006 100644
--- a/actionpack/CHANGELOG
+++ b/actionpack/CHANGELOG
@@ -1,5 +1,14 @@
 *SVN*
 
+* Add Mime::Type convenience methods to check the current mime type. [Rick]
+
+  request.format.html? # => true if Mime::HTML
+  request.format.jpg?  # => true if Mime::JPG
+
+  # ActionController sample usage:
+  # the session will be disabled for non html/ajax requests
+  session :off, :if => Proc.new { |req| !(req.format.html? || req.format.js?) }
+
 * Performance: patch cgi/session to require digest/md5 once rather than per #create_new_id.  [Stefan Kaes]
 
 * Add a :url_based_filename => true option to ActionController::Streaming::send_file, which allows URL-based filenames.  [Thomas Fuchs]
diff --git a/actionpack/lib/action_controller/mime_type.rb b/actionpack/lib/action_controller/mime_type.rb
index 79da49e789b97..17b3d861ec47d 100644
--- a/actionpack/lib/action_controller/mime_type.rb
+++ b/actionpack/lib/action_controller/mime_type.rb
@@ -139,6 +139,16 @@ def ===(list)
     def ==(mime_type)
       (@synonyms + [ self ]).any? { |synonym| synonym.to_s == mime_type.to_s } if mime_type
     end
+    
+    private
+      def method_missing(method, *args)
+        if method.to_s =~ /(\w+)\?$/
+          mime_type = $1.downcase.to_sym
+          mime_type == @symbol || (mime_type == :html && @symbol == :all)
+        else
+          super
+        end
+      end
   end
 end
 
diff --git a/actionpack/lib/action_controller/session_management.rb b/actionpack/lib/action_controller/session_management.rb
index 60b0cd5f94e40..24f1651b0083c 100644
--- a/actionpack/lib/action_controller/session_management.rb
+++ b/actionpack/lib/action_controller/session_management.rb
@@ -61,6 +61,10 @@ def session_options
       #   session :off, :only => :foo,
       #           :if => Proc.new { |req| req.parameters[:ws] }
       #
+      #   # the session will be disabled for non html/ajax requests
+      #   session :off, 
+      #     :if => Proc.new { |req| !(req.format.html? || req.format.js?) }
+      #
       # All session options described for ActionController::Base.process_cgi
       # are valid arguments.
       def session(*args)
diff --git a/actionpack/test/controller/mime_type_test.rb b/actionpack/test/controller/mime_type_test.rb
index 65acbbf36e64a..0755f9d62d4c8 100644
--- a/actionpack/test/controller/mime_type_test.rb
+++ b/actionpack/test/controller/mime_type_test.rb
@@ -1,8 +1,8 @@
 require File.dirname(__FILE__) + '/../abstract_unit'
 
 class MimeTypeTest < Test::Unit::TestCase
-  Mime::PNG   = Mime::Type.new("image/png")
-  Mime::PLAIN = Mime::Type.new("text/plain")
+  Mime::Type.register "image/png", :png
+  Mime::Type.register "text/plain", :plain
 
   def test_parse_single
     Mime::LOOKUP.keys.each do |mime_type|
@@ -30,4 +30,18 @@ def test_custom_type
     end
     Mime.send :remove_const, :GIF
   end
+  
+  def test_type_convenience_methods
+    types = [:html, :xml, :png, :plain, :yaml]
+    types.each do |type|
+      mime = Mime.const_get(type.to_s.upcase)
+      assert mime.send("#{type}?"), "Mime::#{type.to_s.upcase} is not #{type}?"
+      (types - [type]).each { |t| assert !mime.send("#{t}?"), "Mime::#{t.to_s.upcase} is #{t}?" }
+    end
+  end
+  
+  def test_mime_all_is_html
+    assert Mime::ALL.all?,  "Mime::ALL is not all?"
+    assert Mime::ALL.html?, "Mime::ALL is not html?"
+  end
 end
\ No newline at end of file
diff --git a/actionpack/test/template/form_tag_helper_test.rb b/actionpack/test/template/form_tag_helper_test.rb
index e7fd3b082383c..cc5ab1e7f4282 100644
--- a/actionpack/test/template/form_tag_helper_test.rb
+++ b/actionpack/test/template/form_tag_helper_test.rb
@@ -132,7 +132,7 @@ def test_stringify_symbol_keys
 
   def test_submit_tag
     assert_dom_equal(
-      %(<input name='commit' type='submit' value='Save' onclick="this.disabled=true;this.value='Saving...';alert('hello!');return (this.form.onsubmit ? this.form.onsubmit() : true)" />),
+      %(<input name='commit' type='submit' value='Save' onclick="this.disabled=true;this.value='Saving...';alert('hello!');return (this.form.onsubmit ? (this.form.onsubmit() ? this.form.submit() : false) : this.form.submit())" />),
       submit_tag("Save", :disable_with => "Saving...", :onclick => "alert('hello!')")
     )
   end