Synthesis tool free-source
I personally use an open source simulator (iverilog) in combination with manufacturer supplied toolchains (xilinx ise, altera quartus).  The verilog code I write avoids FPGA specific primitives so that it can be simulated with open source tools and then ported to whatever FPGA I need to run it on.  The manufacturer's tools are pretty much the best you can get for most of the parts out there.  Now, I use FPGAs that are large enough to require licenses for the software, but if you stick to the smaller FPGAs and don't need any of the vendor-supplied IP cores, then the free versions of the tools work just fine (generally the only restrictions on the free version are the supported devices, IP library, specialized features like floorplanning and partial reconfiguration, and on-chip debugging features).  

There are some open source tools for synthesis/place and route, but the device support for these are extremely limited.