This online photo editing tool has a Touch Up suite! 15 cool effects like Sunless Tan, Airbrush, and Lip Color to guarantee that every picture shows your best side. Goodbye shine, goodbye wrinkles; hello Mascara, Blush, and Highlights! Advanced Tools (Dodging and Burning) keep shadows off faces and make spotty lighting consistent.
Check it out: http://www.picnik.com/ Be sure to pay attending to the loading messages!
There's a whole section for Halloween in the premium edition ($25/yr):
Plus with the premium edition- you also get unlimited access to all your favorite photo websites right from inside Picnik, including Photobucket, Flickr, Picasa Web Albums, and Webshots, which gives you the ability to transfer photos to and from those different sites, to and from Facebook!