The Romance of Tristan Resources
This website gives background on the early versions of the Tristan story. It also includes a nifty chart showing the genealogy of Tristan's family, the House of Cornwall.
Want to read all about the origins of the Tristan story, including its retellings up until the present day? Take a look at the Camelot Project, which also has a bunch of artistic renderings of the legend and a bibliography if you just can't get enough of this stuff.
Movie or TV Productions
This film version stars James Franco as Tristan and Sophia Myles as Isolde (Yseut). Proof that the legend is still hot.
A filmed production of the Wagner opera. This story was totally meant to be an opera.
An Italian made-for-TV movie based on the legend as edited by Joseph Bédier. How could a love story this juicy not become a made-for-TV movie?
Part of the alternative "courtly" Tristan tradition, Gottfried von Strassburg's version of the legend was written around the same time as Béroul's. The Wagner opera was based on this famous retelling, so it's worth taking a look to see how this baby compares to Béroul's.
Malory's Morte d'Arthur contains one of the most famous retellings of the Tristan story, in which Tristan is actually a knight of the Round Table and a great favorite of Arthur and his other knights. See Book 8 for the Tristan story. You know you want to. (Need some help with it? We've got you covered.)
Preview of the 2006 movie starring James Franco and Sophia Myles.
Here's a video of an aria sung by the character of Isolde in the Wagner opera.
See this list for links to the mother lode of images of Tristan and Yseut in art, most of them from the late 19th to early 20th century.
Another list of Tristan and Yseut in art, this time with thumbnails of the images included for easy skimming.