This section contains major SPOILERS.
I do not recommend to read on if you have not seen the movie at least one time...
Andy Klein's Memento Analysis
A first detailed plot analysis of Memento was published in June 2001 on salon.com. As Klein wasn't able to answer all the questions that arised he has returned to answer some responses to his article.
Movie "Memento" Plot FAQ
This site discusses pros and cons for various solutions and ideas for Memento.
Highly recommended but unfortunately discontinued.
Memento Secrets: Memory is treachery
Trivia for the film & my own personal thoughts about Memento.
About Car licenses, subliminal messages and insulin injections.
Official Memento Website
The Official Memento Website was created by Christopher Nolan's brother Jonathan and gives some background information that accompanies the movie. It might give you some clues but won't give away too much if you haven't seen the film yet.
Jonathan Nolan's short story 'Memento Mori'
Christopher Nolan's script was inspired by an idea his brother Jonathan had for a short story. The two brothers developed both story and script mostly independent from each other. So Jonathan's story, published in Esquire magazine is quite different but nonetheless interesting.
Memento Final Shooting Script
The complete screenplay downloadable as a word or as a text-only version.
Download: Adobe Acrobat Version (255 kB) | Text-Only Version (279 kB)