In past years I have made a song sheet for the seder, containing the sheet music for nearly all of the seder's singing and chanting (this excludes most of the Magid). My sources for these tunes are mostly the ones listed in the Nusach site, with special credit to Virtual Cantor, Siddur Audio, and a recording of Cantor Pinchas Rabinovitz, all of whose mp3s have taught me a great many wonderful melodies that I've included. In 2011 I also recorded myself singing it all, for the benefit of those who want to learn the seder's music in the car, say. You can find it as one .zip file or download the individual mp3 tracks.
Each year, I made a different songsheet. I started out knowing very little of the seder, and over the years I've learned more and more, and the songsheet has evolved appropriately. Of note, in 2008 I was able to find other singers who would sing in harmony with me, so I wrote some 4-part arrangements. Also, in 2015, I led the entire seder in Hebrew, and while I didn't notate all of the nusach, I did notate much of it in the leader supplement. I didn't lead a seder in 2013, and in 2014 I just used the 2012 songsheet.