If you darken your hair, or go red, instead of lightening, it might be worth your time to play around with Manic Panic. I mix Cobra and Infrared 6:1 and the result is a dark strawberry blonde, similar to what henna achieves. I keep it diluted in a bottle of conditioner (about 6:1 again) and refresh it in the shower every time i wash. It is the cheapest solution i have found to date, and because it's dilute it doesn't stain hands or porcelain.

If you go lighter, i can't help :(