Robotics/Electronics Class - How Would You Do It?

MainerDood asks: "I have been teaching programming and networking at the high school and collegiate levels for several years, and now I am branching out into electronics and robotics for my high school students. I am keen on Linux and Open Source solutions where feasible, and would like to avoid using pre-packaged robotics/electronic 'kits' (ie: Lego Mindstorm). I have a minimal budget, like to tinker and have access to tons of old PCs... I would like to use them in these projects and buy the 'parts' where needed. I am envisioning an order of breadboards, diodes, resistors, etc. but not sure from where I should order, what a good basic startup setup should contain and resources I should refer too. I have found a bunch of links online and various resources, but I am curious to know how you would go about this... seasoned veterans and electronics/robotics enthusiasts - I am all ears!"