If you've never done embedded development before I highly recommend the two parts MOOC "Embedded Systems - Shape The World"[1].

The course is well structured, teaching the basics you'll need for those boards that doesn't usually have an OS and requires a ~40$ components kit that include a Texas Instruments board. Quite fun if you follow along and do all the exercises.

[1] https://www.edx.org/course/embedded-systems-shape-the-world-... , https://www.edx.org/course/embedded-systems-shape-the-world-...