Many ERers use a bucket approach, but IMHO many people who have some financial common sense have been doing something similar for a long time. Ray Lucia gave it a name and expanded on it a bit.
I plan to have a simple bucket approach keeping 3 to 5 years in cash and CDs and replenishing that bucket from my stock and bond portfolio in good years and living off the cash in bad years. The cash bucket is just a capacitor or buffer to even out market fluctuations.