alright gang im looking at circuit bending with the arduino but not too sure how to go about doing it. i presume i need some sort of digital to analogue converter to change resistance but where do i get one of these and is there a risk of shorting out the board and the computer??
cheers james.
You can get digital potmeters. It's a chip you can control with SPI interface or otherwise. Just google "digital potmeter.
I did a lot of circuit bending, including a toy that is sequenced from a PC via the parallel port, this was before i knew about Arduino.
http://www.mikmo.dk/cbhabitatintercom.html
You could also use Arduino to "push switches", in a sequencer like way
nice cheers, i thought of using photocouplers or using the arduino to change the brightness of an led onto an LDR. how would i make a switch with the arduino
ive tried using a LRD without any luck any ideas why? is there a specific one i have to buy?
manage to get it working just really slight change in the LDR.
how would i make a switch with the arduino
I think you could use relays.
switch: you can use transistors, i've used 2n2222 to drive a toy drum machine without problems. but remember, if you don't insert a 2k2 resistor between the transistor and the pin you can burn the transistor. this tutorial was usefull for me: http://techhouse.brown.edu/~dmorris/projects/tutorials/transistor.switches.pdf
variable resistors: i prefer to use LRD and leds because it's cheap. i think that digital potentiometers can be more accurate but if you want to circuit-bend you shouldn't care to accuracy. 
ciao
For switching you have (at least ) 4 options
transistors as outlined above
Relays, which i think is overkill for bending, better suitede for high voltage / current circuits.
Analog switch IC's like 4016 / 4066 (like i did see link in my previous post)
Photocouplers which often is the prefered way as it isolates the two circuits from each other.
http://www.rapidonline.com/searchresults.aspx?style=0&kw=2n2222
had a search online, which one should i go for, theres loads of em!
any smal signal transistor would do.
2n2222 2n3904 for instance