SparkFun has been a fan of Arduino for a long time. We've programmed ATMega328s (and 168s, and 8s before that), written tutorials and hacked all sorts of fun projects.Now the market is maturing, and we are looking at a lot more ARM chips. One advantage of the newer chips is that they generally do not need a USB-to-serial adapter; instead they have USB built in (at least the ones we are using do). You still need to add a bootloader to use them with Arduino, and since ARM programmers are also a little more complicated than AVR programmers, you'll want to invest in a stand-alone programmer instead of trying to use the Uno you have laying around.
We wrote a handy guide to help you get started with ARM programming, including a list of recommended programmers and pins, best practices, hardware hookup walk-throughs and software troubleshooting.
We are continuing to look into more and more product options for ARM and AVR programming, so make sure to check back with us or sign up for our newsletter!