A little update to introduce XMR-Stak CPU miner. This was released a short time ago, and it is free ! Although we do recommend to set a small donation % to reward software development. You can check it out on this reddit thread and here for download links.
Performance is nearly identical to the closed source paid miners. Here are some numbers:
I7-2600K – 266 H/s
I7-6700 – 276 H/s (with a separate GPU miner)
Dual X5650 – 466 H/s (depends on NUMA)
Dual E5640 – 365 H/s (same as above)