Websites
Dive on in. This is a good resource for all things Keats: his poems and letters, pictures, biographies, etc.
This is a comprehensive biography of Keats's life—good stuff.
This is an archive of full-color scans of various print editions of The Eve of St. Agnes that you can browse through online or download. It's majorly cool; a lot of these editions are beautifully illustrated and at least a century old.
Get the low-down on the feast of St. Agnes from the folks who know.
The artist Harry Clarke completed a set of stained glass windows, each section of which depicts a scene from The Eve of St. Agnes.
Video
The BBC has of course, bless them, done a documentary on the Romantic poets. Here's the bit that covers the end of Keats's life, complete with period re-enactments and dreamy recitations of his poems.
Audio
Here, have the poem read out loud for you, complete with music and voice actors.
Spanish composer Ramón Humet took a little inspiration from Keats and wrote his own musical interpretation of the poem. It's cool—in an eerie, unsettling way.
Images
This is the title page of the original book in which The Eve of St. Agnes was published, Lamia, Isabella, The Eve of St. Agnes, and Other Poems. In case you're wondering, those "other poems" comprise the bulk of the Odes, the most famous of Keats's poems.
Here's the couple, immortalized by artist William Holman Hunt.
This is Arthur Hughes's triptych depicting the events of the poem—you can see Porphyro sneaking into the castle on the left, Madeline's waking-up scene in the middle, and their final escape from the castle on the right.
Here's the lady herself, St. Agnes, depicted (as per usual) with her halo and lamb.
Life was tough before White-Out. Even though it's not the manuscript for The Eve of St. Agnes, this at least gives you an idea of how Keats edited his own poems and how… totally not legible his handwriting was.
Movies & TV
Bright Star focuses on Keats's relationship with his own sweetheart, Fanny Brawne. It's much like Titanic in that we've watched the first half fifty times and pretend that the second half never happens.