text: I just did this in Oregon and California.  First you have to prepare your Federal return.  You can file for free at TurboTax if you earned less than $50K.  When you put your income in, it asks what states you earned it in.  At the end, it will give you an option to file your state returns as well.  Some states will let you file for free, but TurboTax charges $19.95 to prepare each return.  You can also visit each states website by doing a google search for "california taxes", etc...