http://hlt.media.mit.edu/?p=1229 Programming an ATtiny w/ Arduino
http://hlt.media.mit.edu/?p=1695 Programming an ATtiny w/ Arduino 1.0
These are two MIT low high tech articles on using the arduino environment for programming ATtinys.
However, the first uses tiny45-85.zip which only works with Arduino 0022 (and maybe earlier.
The second uses tiny.zip from github and only works with Arduino IDE 1.0 Mixing them up makes a mess.
Mixing these cores will make a mess! There should be some comment on the Arduino ISP page as the net is littered with avrdude errors caused by this.