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More embedded notes (with some Lua content):

Yes, the LPC2478 is pretty nice.  My brother was looking at using one
at work (no Lua, though), but that project is currently on hold.

Somebody will make a Cortex M3 with an external bus.  The NXP LPC17xx
series (Cortex M3) looks pretty nice; the LPC1768 has 64K RAM, 512K
flash, MAC, USB OTG, 2xCAN, 4xUART, PWM, QEP, etc, but no external

In reality, all the really cool chips are BGA, but those make QFPs
look easy to prototype.  There are companies selling products that
claim to make prototyping with SMT parts easier, such as SchmartBoard,
but I haven't tried them.

Still, ARM MCUs are getting down in size; the STM32F103T8 has 20K RAM,
64K flash in a 36 pin QFN.  But to run Lua decently, you'll need at
least a QFP80 (e.g. LPC1758 with 64K, ST STR911FAM4x with 96K SRAM).
BTW, you always have to read the fine print; for example, in both the
STR9 and LPC238x, the 96K SRAM is also used for the Ethernet buffers,
so if you use the network, you won't actually have 96K available.

Compilers & DSPs: most DSPs need the manufacturer's compilers (I know
TI's do); however, IIRC, the ADI Blackfin DSPs use gcc.  Someday I may
try compiling Lua for a TI C6701 board, but that's not going to happen
for a while.

CAN is a 1Mbps network, so there's no way a UART will work.  You can
add them externally, e.g. via a SPI port.

Finally, because this bugs me, some terminology notes:
SoC - System on a Chip.  So, a chip that integrates almost everything
a piece of equipment (system) needs.  A good example is a highly
integrated chip for MP3 players.
SiP - System on a Package.
MCU - Microcontroller.  A CPU that includes all its memory on chip.
MCUs go back to the very early days, with such chips as the Intel
8042, before the term SoC was ever used.
MPU - Microprocessor.  A CPU that needs external memory (e.g. x86,
Atmel AT91RM9200)

If there really is enough interest, we should start thinking about
starting a dedicated embedded processor Lua mailing list.  Then we can
go off topic without fear!