Electronic – ARM Cortex-M3 development tools

For professional type use, your major options are IAR, Keil or Rowley CrossWorks. Keil is owned by ARM, which may or may not give them a slight advantage. I'd say the performance between IAR and Keil is nearly identical. Rowley is bargain of the 3. Rowley also let's you use cheaper debuggers, such as the J-link. You might be able to use the J-link with IAR as well, but I think Keil forces you to use their Ulink products, which can be a bit more expensive. As far as support, I believe Rowley is purely through their website. IAR and Keil offer 1 year or so of phone support. From what I've been told, Keil seems to offer better support in the US, while IAR is more focused on Europe. I've used Keil without any issues and support was good. That being said, any of these 3 will probably perform just as well.

I've been blogging about the Linux board I've been working on starting here and continuing here. I started thinking I would use a Cortex A8, but eventually settled on the Atmel AT91SAM9G20.

To try to answer your other questions:

• You can see the components I used in my schematic, but I don't know of a more general explanation of why each is necessary.
• The processor is only about 10-20% of the total cost of parts. Assembly is another $4-40, depending on the quantity built. I suspect the profit margin is 30-50%.
• Depending on the package, the OMAP3517 BGA package has either a 1 mm or 0.65 mm ball pitch. Generally, below 0.8 mm pitch, you need to X-ray at least some fraction of the finished boards to check for errors. (Just for the record, the OMAP3517 1 mm packages aren't actually available yet.)

If you have other, more specific questions, I'd be glad to try to answer them.