As has been pointed out before, "making your own" is not exactly possible for the average person. Soldering down 0.5mm pitch SMT stuff is hard even with the right tools, and that assumes you can get your hands on the parts in the first place - a lot of distributors won't deal with individuals/small quantity orders. Add onto that the fact that some stuff like flash and 3.3v EDO ram (as used by the SA1100) is generally on 14 week+ lead times... the PCBs will cost you around $1000 to get made one-off too.

Real homebuilt stuff is really limited to stuff you can get in 0.1" packages - which isn't anything desparately exciting anymore :(

Hugo