There is no punctuation mark I am aware of commonly used to denote sarcasm, but one can use other typographic or orthographic indicators.
One can use italics to signify text that is emphasized differently in speech, e.g.
Did you shut the door?
Well, of course I shut the door. We wouldn't want customers to walk in or anything.
Outside of quoted speech, “scare quotes” may suffice.
We wish him well in his new career as a “waste disposal technician.”
Scare quotes can set apart sarcastic neologisms or compounds words, which could also be indicated with hyphenation or capitalization.
The new product line reflects a certain any-color-as-long-as-it's-black-ism among the company's designers.
What better way to close the film's contrived plot than with a Beam Me Up Scotty moment?
Wheeeeeeee! Another season of Idol!
In online chats or other informal communication, one could also employ a range of emoticons, text art, or similar visual tropes.