I second the recommendation on the Cactus system, but I use the Cactus V6's - I use one to fire a Canon 580EX from my Fuji X100 and it's great - reliable, easy to use, and reasonably affordable for two transceivers.
The thing that sets the 6 apart, though, is that you can remote control the power output of the flash from the transceiver on your camera - you set the speed light to E-TTL mode and then it's fed the power level from the Cactus unit on it, which you can control manually from full power on down in 1/10 stop increments right from your camera. It's super helpful if you're out in nature somewhere and you prop your speed light on some rock somewhere as a backlight, you don't need to keep walking over to it to adjust the power, you can do it remotely. Took a little testing to get it running but now it works great.
It also lets you mix-and-match units - you can control Nikon, Canon, and whatever other brands all simultaneously and independently control the power on each. It's pretty cool.
I think if you're using Yongnuo speed lights then the Yongnuo triggers are the way to go as a complete system, and from what I've read it's really good, but if you're looking to use different brands with the Fuji and control the power outputs remotely I know the V6 is solid.
