Textbooks we have:

Lowe Chapter 1
Course Companion pp. 204-215

Podcasts: this is very good and is produced specifically for IB students.
Mr. Allsop's podcasts on the lead up to WWI. Also specifically for IB students.

Serious Videos:

Crash course world history: Part 1: How WW1 Started Part 2: Who started WW1

Fun Videos:

Causes of WW1 rap battle
Horrible Histories: Song - WW1 cousins
Horrible Histories explanation of the causes of WWI

Interactive map:

The Map as History- Europe plunges into war (a good overview of the opening moves)


The July Crisis - a good blow-by-blow of the lead-up to the war
First World War: The July Crisis article by William Mulligan (History Today)


Niall Ferguson Interview with Allan Gregg explaining his re-interpretation of the causes of WW1 (he pins responsibility on Britain). High level.
Dunn's History Notes (good discussion of the causes of WW1). Higher level.
Cool interactive from BBC for basic info
John D. Clare site - for British high school students
John D. Clare site that explain historiography of the causes of WWI
BBC article: 10 interpretations on the causes of WW1