Just a shout-out about the Icestorm project which provides a complete open-source toolchain for Lattice's iCE40 FPGAs. It's mostly the work of one guy (Clifford Wolf): http://www.clifford.at/icestorm/.

It's worth noting that arachne-pnr (https://github.com/cseed/arachne-pnr) is written by a different person (Cotton Seed).