Are you interested in the Raspberry Pi Pico and Arduino? While I've heard rumors are about the possibility of a Raspberry Pi RP2040-based Arduino, I haven't seen one in the real world. This is also true for official support by Arduino for their framework. Thankfully, Earle F. Philhower III (earlephilhower on GitHub) provides us with an unofficial integration for the Arduino framework. At his GitHub repository, you will find the code and instructions for the Arduino IDE integration. All major peripherals seem to work even if the current version is below 1.0. If you encounter any bugs, you can report them. Also, if you make additions, report them back so we all can benefit from your contribution.
 
Raspberry Pi Pico in Arduino IDE

Pico in Arduino IDE

This is great news. As you wait for the Arduino guys to present their official support and boards, you can already use many of the existing Arduino libraries and code with the Raspberry Pi Pico. As a benefit, the code earlephilhower provides also integrates a ready-to-use toolchain. With the integrated toolchain, the major operating systems are supported.

The GitHub repository provides a quick starting guide how you can integrate the Raspberry Pi Pico in your Arduino environment. All the major components like SPI, I²C, UARTs, ADC and PIO are supported. As these have not intensify tested, there may be some rough edges left. So, if you encounter any bugs, report them back. Or, if you fix them, share your changes with the community.
 
Raspberry Pi Pico with pin header

Give It a Go

For those still struggling if they should use a Raspberry Pi Pico for their next project: If you do not need Wi-Fi give it a try. Also, as the Raspberry Pi Pico comes without any attached or included pin header, have a look at the latest creation from Elektor, a Raspberry Pi Pico with pre-assembled pin header and USB cable in a nice appealing box.