You can download the files from this link http://hlt.media.mit.edu/?p=1695 I found it easier to leave the folder inside the Arduino's hardware folder, but you can use whichever method suits you best. Make sure you install the support for Arduino 1.0, for it is the one that has support for SPI, i2c, and NewSoftSerial...you will need to set the ATTiny's fuse settings to 8MHz which can be done by selecting "ATTiny85 8MHz" from the boards menu and clicking "Burn Bootloader" (it wont burn a boot loader, but set the fuses to 8MHz)..let me know if you have trouble...Ill try to get a video up
Cheers!
Mr_E