Well, you certainly have your work cut out for you. Hacking together hardware isn't quite the same as software, because mistakes are expensive. Debugging noise on a signal line with an oscilloscope takes eons compared to watching a value in memory. And if it's a significant screw-up you've got to re-spin the PCB which costs real $$. Hell I have an EE degree and I still find it annoying as crap.
If you're looking at running Linux, don't bother with your own PCB. Even the smallest possible system that runs that is going to be using high-speed data lines, processors with 100+ pins, multi-layer boards...it's just not something you worth spending your own time on. Get one of the development boards people are mentioning here.
However, don't assume something like the Picwing needs to run Linux and Flash and WiFi. Companies like Microchip, TI, and Freescale sell processors that run in the $5-$10 range and have their own built-in code memory and RAM. These things are programmed in C, and although being way less powerful, are more than capable of running a basic TCP/IP stack and graphics/touch library once you learn to think outside of having an operating system. You interface them with external components such as an LCD display, Ethernet or WiFi controller, and an SD card or USB stick for extra storage (or stand-alone serial flash chip, depending on your needs). Microchip for example also provides software libraries that handle things like the TCP/IP stack, graphics/touch interface, FAT file system, etc, and I believe the competitors do the same. (Disclaimer of sorts: I used to work for Microchip and wrote parts of those libraries, so I'm most familiar with their stuff. When I left Microchip's graphics library was limited to QVGA, but I'd imagine either they or a competitor has stepped that up recently.)
Reason I mention this is that this is the cheap way to go if/when you want to get towards mass-production. You can go ahead and develop on the expensive dev boards with Linux while you get the interface right and figure out the business model, but plan to hire someone to design custom HW the right way when you want to do volume. China and India are full of design shops that do nothing but clone iPhones all day long...I'm sure someone around here has a few contacts that could get this done cheap once you can specify exactly what you want.
If you're looking at running Linux, don't bother with your own PCB. Even the smallest possible system that runs that is going to be using high-speed data lines, processors with 100+ pins, multi-layer boards...it's just not something you worth spending your own time on. Get one of the development boards people are mentioning here.
However, don't assume something like the Picwing needs to run Linux and Flash and WiFi. Companies like Microchip, TI, and Freescale sell processors that run in the $5-$10 range and have their own built-in code memory and RAM. These things are programmed in C, and although being way less powerful, are more than capable of running a basic TCP/IP stack and graphics/touch library once you learn to think outside of having an operating system. You interface them with external components such as an LCD display, Ethernet or WiFi controller, and an SD card or USB stick for extra storage (or stand-alone serial flash chip, depending on your needs). Microchip for example also provides software libraries that handle things like the TCP/IP stack, graphics/touch interface, FAT file system, etc, and I believe the competitors do the same. (Disclaimer of sorts: I used to work for Microchip and wrote parts of those libraries, so I'm most familiar with their stuff. When I left Microchip's graphics library was limited to QVGA, but I'd imagine either they or a competitor has stepped that up recently.)
Reason I mention this is that this is the cheap way to go if/when you want to get towards mass-production. You can go ahead and develop on the expensive dev boards with Linux while you get the interface right and figure out the business model, but plan to hire someone to design custom HW the right way when you want to do volume. China and India are full of design shops that do nothing but clone iPhones all day long...I'm sure someone around here has a few contacts that could get this done cheap once you can specify exactly what you want.