People mentioned the siFive option, but that's a microcontroller. If you were looking for a 64 bit processor implementation, without having to use an FPGA...
It looks like the first dev board that would be capable of running linux will likely be the lowRISC project.
"We are expecting to crowdfund an initial instantiation of the lowRISC platform during the course of 2017"http://www.lowrisc.org/
I'll buy a LoweRISC as soon as they have something for sale (and I have one of the first HiFive1s). But at the rate both organisations are progressing I expect to be able to get a quad core 1.6 GHz 64 bit RISC-V "Pi-like" board from SiFive before LowRISC. Possibly even this year. I've gathered from other things they've said that they're sampling wafers with that SoC about now.
It looks like the first dev board that would be capable of running linux will likely be the lowRISC project.
"We are expecting to crowdfund an initial instantiation of the lowRISC platform during the course of 2017" http://www.lowrisc.org/