Websites
The late professor Jane Zatta has compiled a boatload of background information on the "Clerk's Tale," including images and letters between Chaucer's sources and contemporaries dealing with the tale's reception.
This page collects links to several of Chaucer's probable sources for his tale as well as a French version of the Grisilde story via Boccaccio (the "Goodman of Paris"). It also links to a bibliography of contemporary scholarship on the "Clerk's Tale," if that's your shtick.
Video
Okay, no, it doesn't have much to do with the Clerk or Grisilde, but A Knight's Tale's got a young Chaucer in the cast (played by Paul Bettany), giving great speeches like this one.
Historical Documents
Here's the portrait of the Clerk from the Ellesmere Chaucer, a highly decorative Chaucer manuscript widely considered to be one of the most beautiful.
Want to see an old manuscript version of the "Clerk's Tale"? Look no further. Here are the first pages of the "Clerk's Tale" in the Ellesmere Manuscript.
Boccaccio's tale (through a Latin translation by Petrarch and French by Philippe de Mezieres) is Chaucer's source for the "Clerk's Tale." This English translation comes from Decameron Web, a great website if you're interested in learning more about Boccaccio and the Decameron.
In this letter to Boccaccio, Petrarch describes his enjoyment of the tale of Griselda, his knowledge of its reception among his contemporaries, and why he decided to translate the tale into Latin.
Audio
There are tons of operas based on the story of Grisilde. Here's one by Vivaldi, (loosely) based on Boccaccio's version of the story from the Decameron.
Images
In or around 1493-1500, an artist known only as the "Master of the Story of Griselda" painted a series of three panels depicting events from the last tale of Boccaccio's Decameron, the "Story of Patient Griselda" (Chaucer's "Clerk's Tale" is based on the Latin translation of this). That's right: there's someone out there known only for his painting of this one story.
The Master of the Story of Griselda wasn't the only Renaissance artist to get some inspiration from Grisilde's trials: Masters Pesellino and Apollonio di Giovanni also painted scenes from Boccaccio's story.
Grisilde inspired artists right up until the nineteenth century. Here's a portrait of her by Frank Cadogan Cowper. Which Grisilde comes closest to how you saw her? Any of them?