leaflabs.com: "Maple (Rev5)
This board has all the essentials: a fast processor with lots of peripherals. At Maple’s core is a 72MHz STM32 processor, an ARM Cortex M3 chip. In the past, ARM processors were notoriously unfriendly to non-professionals, due to proprietary tool chains, unfamiliar instruction sets, and impenetrable supporting literature. LeafLabs has changed this for Maple by providing a complete ARM platform, built from open source components, which includes an intuitive programming environment and friendly, thorough documentation.
For all the Arduino lovers out there, Maple is offered in an Arduino-compatible format, complete with an Arduino pin layout and programming environment. Maple is a great way to get started with an advanced 32 bit processor that, until now, has principally lived in the commercial domain. Take your projects to the next level with Maple’s fast clock, sophisticated interrupt architecture, and loads of built-in peripherals."