Matt Bruenig at Demos has spreadsheet/map (disposable income) of least egalitarian states, with the most inegalitarian ten all in South and Southwest, with New Mexico, Arizona, California in the top three. He concludes thus about the ventiles (ventile=1/20)and percentiles (see @billmon1 for nice map):

Mississippi is quite poor. In both equivalized and per capita income, Mississippi is in last or second-to-last place for every ventile except the 5th percentile in equivalized income where it is in third-to-last place.

New Hampshire outperforms everywhere except the top. In both equivalized and per capita income, New Hampshire is ranked number one at every ventile until you get to the 70th or 75th percentile, at which point it gives way to New Jersey and Connecticut. Even at the higher percentiles, however, New Hampshire remains in the top 5 or 6 states.

Vermont is the most equal. In both equivalized and per capita income, Vermont has the lowest P90/P10 ratio, the second-to-lowest P90/P50 ratio (behind Minnesota), and the lowest P50/P10 ratio.

New Mexico is the least equal? In equivalized income, New Mexico has the highest P90/P10 ratio, the highest P90/P50 ratio, and the second-to-highest P50/P10 ratio (behind Arkansas). In per capita income, New Mexico has the highest P90/P10 ratio, the highest P90/P50 ratio, and the fourth-to-highest P50/P10 ratio (behind Mississippi, Louisiana, and Oklahoma in that order).