I've recently acquired a Motorola A780 quad-band GSM cellphone. It's basically an Intel PXA270 based system with 48MB flash, a 256MB TransFlash reader, Bluetooth, a GPS receiver and MotaVista CEE Linux 3.0 (2.4.20 based).
As usual, the vendor tries to "lock down" the OS from the user. Luckily, some nice people of motorolafans.com have already found their way into the phone. Using their "linloader", you can put shell scripts on the TransFlash card and execute them by clicking on them in the explorer. Using that you can put the phone into a mode where it runs as usbnet 'device' with telnetd and samba.
By now I've already learned quite a bit about the phone. Interestingly, they are running glibc (not uClibc). The same goes for the rest of the device. No busybox, but rather the standard gnu programs. So it's much less of the typical embedded Linux environment, and more like a "regular" GNU/Linux system.
glibc-2.3.2, embedded QT, and some "ezx" class library on top. Add some J2ME runtime environment, a handful of different filesystems (vfat, cramfs, romfs, TrueFFS, mfs), a SD/MMC reader driver, a GPRS module, some strange "USB Logger" (looks like syslog-over-usb) and a number of userspace programs and there you go.
Oh, and yes, obviously the phone was delivered with no GPL license text, no source code and no written offer thereof. But that's a different chapter.