Andrew Gelman ponders the objects of the class "Foghorn Leghorn", in which the parody (Leghorn) remains famous while the topic being parodied (Senator Claghorn) becomes forgotten.
What are other members?
I will defer to others more familiar with their work, but could one put Gilbert and Sullivan in this class?
Gulliver's Travels is a good general parody, but in its day was it referring to something specific?
Update, from Wikipedia: "as Gulliver's Travels was a transparently anti-Whig satire it is likely that Swift had the manuscript copied so his handwriting could not be used as evidence if a prosecution should arise (as had happened in the case of some of his Irish pamphlets). In March 1726 Swift travelled to London to have his work published; the manuscript was secretly delivered to the publisher Benjamin Motte, who used five printing houses to speed production and avoid piracy. Motte, recognising a bestseller but fearing prosecution, simply cut or altered the worst offending passages (such as the descriptions of the court contests in Lilliput or the rebellion of Lindalino), added some material in defence of Queen Anne to book II, and published it anyway." (thanks to Bill Jefferys comment on Gelman's blog)
Farther afield -- given Arthur Conan Doyle's fascination with spiritualism, I'm tempted to treat my beloved Sherlock Holmes stories as parodies. I'm referring particularly to the introductory part, in which Sherlock makes uncannily accurate predictions about the person based on thin visual evidence right after he meets them. Was this not so much a nod to the powers of science (which is what I thought when I read them in high school) as a parody of scientific over-reaching -- which he had to keep repeating because that's the portion of his writing that people liked best?