i have an old radio shack usb to serial cable, it was sitting in a box for the last few years because the drivers did not work in vista/windows7 64 bit, i ended cutting the board out of the cable and started looking up parts. after looking up the prolific chip i realized i could remove the eeprom and use the prolific drivers in win7. it kinda upset me cause all the parts on the board are really cheap. anyway I'd love to see a sub $10 usb > rs232 adapter. ill prototype it if enough people are interested.
absolutely ill share. i'm still learning eagle and need some pointers, what i have is still pretty crude but ill put some links and post the beginnings a little later today. just let me know what thread you want it in.
i have looked at the pcengines boards before, i believe the size is about 6 times the size of the WPv2 and probably use much more power than is being shot for.
i have come up with a parts list loosely based of atmel at91sam9260 reference design and have most of the major parts at about $35 in single quantity. and about 22-25 in runs of 100.
i avoid hot air like the plague, unless the bottom pad is needed as heat sink. I use no clean flux on board and bottom of chip and with small tip roll over solder on about half of pins and push excess to other half of pins. stereo microscope is very helpful.
gyros tend to be a little out of reach for shoestring budget projects, they have a 9DOF board that is ridiculous but all 3 chips share the same IIC bus. all of thoes QFN packages are hard to solder. silabs.com has a good tips and hints page for manually soldering them. as all but 2 of their micros don't have dip versions.