Written by Cassandra Claire (presently known as Cassandra Clare, author of The Mortal Instruments) and posted in the Internet via FanFiction.net and later FictionAlley.org, The Draco Trilogy is hailed (at least by this blogger) as the fanfiction of all Harry Potter fanfictions.
It was so popular back then that some readers prefer reading this fan novel rather than the canon one written by Queen J.K. Rowling. So much so that others even wrote stories based on the trilogy which is based on the world wide 7 part phenomenon. And yes, that is weirdly confusing, I admit.
The Draco Trilogy is composed of three novel length stories which are as follows
Draco Dormiens - An accident in Potions class led to Harry and Draco exchanging bodies, thus, opening a whole alternate universe where the two are alternately allies and enemies battling inner and outer forces of evil.
Draco Sinister - Both likely and unlikely hero rage war against Wizarding History's greatest antagonist.
Draco Veritas - The conclusion to the epic series. Very long read, I must add.
The stories were taken down the internet upon the author's request, following a fanfiction-community-wide plagiarism scandal and CC's leap to professional published fiction, but not before PDF files (complete with fanart from different artists) were made available for legitimate download. Nowadays, it's hard to find copies of said PDF's but not impossible if you know where to look.
And I'm proud to say you have stumbled upon a goldmine.
I lost my original copies a while back after repeated re-installment of my computer's OS, but 'lo and behold, a kind heart decided to upload their copy for everyone's sake and I was able to download another copy via these links:
(Stanza Ipod Touch Screencaps of Draco Sinister)
I have no opinion regarding the controversy surrounding this fan made novel. All I know is that reading it is keeping the Harry Potter spirit alive in my mind, especially now that the epic series has published its last sentence. All we have to look forward to now is the 7th movie split in two, and with the screaming and fainting-over-lead-actor-hotness vampire wannabes trying to steal the spotlight, I do miss those times when quality literature took over pop culture and not sex crazed half-human mutants and a masochistic protagonist.