This answer record provides links to Xilinx Development Boards/Kits and TRDs. Xilinx Development Boards links provide example design files for respective cores, a ready to download bit file, and instructions on how to generate the core and implement the generated example design.
This article is part of the PCI Express Solution Centre.
(Xilinx Answer 34536) - Xilinx Solution Center for PCI Express
PCI Express Example Designs
Boards and Kits
Targeted Reference Designs and Connectivity Kits