It's still a work-in-progress, but there should be some interesting news at the RISC-V Zurich conference next week [1]. For example, Imperas has announced an ISA simulator for the current 0.71 version of the specification [2].

[1] (https://tmt.knect365.com/risc-v-workshop-zurich/agenda/1)

[2] (http://imperas.com/articles/imperas-delivers-first-risc-v-si...)