I ported uClinux to the Sony PSP (check it out at http://df38.dot5hosting.com/~remember/chris/. It wasn't on slashdot because they had more important stories to run, like what operating systems the iPhone DOESN'T run. But I'm not bitter
Anyways, this project was a major pain in the ass, and at the moment its kind of stalled. The problem is that the hardware design is closed, and most of the components are all consolidated onto one giant Sony ASIC so inspecting the motherboard is no help.
So... It took a million years just to get the memory map right, and understand the exception/interrupt plumbing of this customized not-quite-MIPS-R4400 cpu core, and understand how to talk to the video, serialport, cache controller, etc.
Now, I happen to know at least 10 people who would buy a PSP if it had a really well supported linux. Allowing people to target a popular platform, rather than a proprietary one, would allow really neat applications that made use of this things built-in Wifi/Audio/etc. In short, if it was an open platform, it would allow for better interoperability, more diverse applications, blah blah blah. And if its Truly Truly "open", people could even make new PSP's that maintained compatibility with current PSP software, but optimized it for other tasks, etc. Whatever, you name it.
Of course, Sony is a content company. The memory stick interface, from which you can launch applications, makes one think "Maybe I can write some software to dump my friend's UMD game to memory stick, and then launch that game from the memory stick, so I can copy it." But thats REMARKABLY difficult on the PSP because they will only run memory stick code that is cryptographically signed by Sony (unless buffer overflow exploits are used, etc. which exist and are what make uClinux/PSP possible) and due to the closed nature of the platform, I don't think anyone even knows how to get a signed copy of a UMD onto a memory stick.
So it works pretty well for Sony. And it stinks for me.