The "development system" I have made for myself is nothing else than a CPU foot with a reset circuit and oscillator, a simple power supply with regulated 5V and 12V outputs and all I/O lines wired to box headers. There's a MAX232 and MAX 485 that can be used (or not) by just settings some jumpers. From there, I either wire it to a breadboard or make a small "dedicated" PCB (wire-wrapped or home-cooked copper) that fits directly into the headers. Just because it's so bloody simple I can use it for almost any project and gets me started within no-time. After a couple of projects, you will have a box full of handy "add-on" boards that can serve for new projects, either with or without modifications. It works good for me so I can recommend this approach.