Here are some of the standard reference texts on matroids and oriented matroids.
It is probably not necessary to look through any of these before the summer school;
they are only here in case the reader wants to know more about the topics mentioned in the surveys.
Here are some (relatively) recent papers that represent a few trends/threads/developments
of interest (to me).
In most cases only one paper about a topic is listed, but the interested reader can find more related references within it.