I finally got around to actually testing the above circuit and it works perfectly! I used a seperate power supply for the motor, because my program slows down when everything runs off of my old battery. I got the impression that my communication routines take much longer when the motor is on, and I suspect this is due to undervoltage (I will post results with a new battery). Anyway I just wanted to finally thank you all for the great help and links, especially Darrel for his great transistor explanation...
While searching for schematics and layout programs I did stumbled upon eagle (http://www.cadsoft.de/). I've started using the free version which is limited to 4 x 3.2 inches, two signal layers, and one sheet for the schematics.... Doesn't seem that hard to learn because there's lots of good tutorials out there (for example on programming new parts etc) and there's a lot of downloadable parts libraries. It can output in a lot of formats (some for 3rd party board production, some vector formats for home etching, and also there's a ULP addon for producing G-code directly), but it doesn't do any simulation. I prefered the graphics of the schematic layout on IVEX Windraft (color contrast makes it easier to follow and nicer for web publishing..) and I'm not sure if there's a lot of eagle users in the US, but if you're looking for a solid program that will probably be around for quite some time you could give it a shot...
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