There are hundreds of schematics and working ideas that you can find on google about unipolar stepper drivers. If your into microchips like pic or atmel, you can make a driver with which you can control up to 8 motors at the same time
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I went with this one:
http://www.hobbycnc.com/products/hob...er-board-kits/
It was a great project and it took me about an hour to put everything together.
I took the 4 motor version and with shipping, payed about 105$. And i have to say, it is worth every penny
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And anyway, getting all the stuff you need to make a good and reliable stepper driver you could, maybe, save about 20% from what this kit casts. Getting it all in one package was worth the 20%
You could also salvage the stepper drivers from printers. They also use the all-in-one package types. They are not so powerful, but could be of use....it depends on the project.
Or if you want to play with your own design and make something new, just post your questions here and we'll just have to make it work