There is a short introduction by Mikhalkin: http://arxiv.org/abs/0709.1049 expanded in more detail in this book: http://www.math.toronto.edu/mikha/book.pdf (the link is now outdated; this may be the same book: https://www.math.uni-tuebingen.de/user/jora/downloads/main.pdf  )

The Oberwolfach lecture notes by Itenberg, Mikhalkin and Shustin are also nice.

There is a short introduction by Mikhalkin: Introduction to Tropical Geometry (notes from the IMPA lectures in Summer 2007) expanded in more detail in this book: http://www.math.toronto.edu/mikha/book.pdf (the link is now outdated; this may be the same book: Mikhalkin and Rau - Tropical Geometry.)

The Oberwolfach lecture notes by Itenberg, Mikhalkin and Shustin are also nice.

There is a short introduction by Mikhalkin: http://arxiv.org/abs/0709.1049 expanded in more detail in this book: http://www.math.toronto.edu/mikha/book.pdf

The Oberwolfach lecture notes by Itenberg, Mikhalkin and Shustin are also nice.

There is a short introduction by Mikhalkin: http://arxiv.org/abs/0709.1049 expanded in more detail in this book: http://www.math.toronto.edu/mikha/book.pdf (the link is now outdated; this may be the same book: https://www.math.uni-tuebingen.de/user/jora/downloads/main.pdf )

The Oberwolfach lecture notes by Itenberg, Mikhalkin and Shustin are also nice.