How can I customise memoir's index to have more than two columns?

^{Sorry for ressurrecting an old thread, but I'd like to provide another suggestion for completeness' sake. :)}

The most recent version of the imakeidx package is memoir-compliant. We can easily use it to customize our index, including the number of columns. :)

documentclass{memoir}

usepackage{imakeidx}[2012/05/09]
makeindex[columns=3]

begin{document}

chapter{Hello}

Some text.index{Apple}index{Apricot}index{Avocado}index{Banana}
index{Bilberry}index{Blackberry}index{Blackcurrant}index{Blueberry}
index{Currant}index{Cherry}index{Cherimoya}index{Clementine}
index{Date}index{Damson}index{Dragonfruit}index{Durian}
index{Eggplant}index{Elderberry}index{Feijoa}index{Gooseberry}
index{Grape}index{Grapefruit}index{Guava}index{Huckleberry}
index{Jackfruit}index{Jambul}index{Kiwi fruit}index{Kumquat}
index{Legume}index{Lemon}index{Lime}index{Lychee}index{Mandarine}
index{Mango}index{Melon}index{Nectarine}index{Orange}index{Peach}
index{Pear}index{Pitaya}index{Physalis}index{Plum}index{Pineapple}
index{Pomegranate}index{Purple Mangosteen}index{Raisin}index{Raspberry}
index{Rambutan}index{Redcurrant}index{Salal berry}index{Satsuma}
index{Star fruit}index{Strawberry}index{Tangerine}index{Tomato}
index{Ugli fruit}index{Watermelon}index{Ziziphus mauritiana}

printindex

end{document}

The output:

Use the idxlayout package. It allows for indexes with more than two columns and is responsive to the index-related options and commands of the memoir class.

Disclosure: I'm the package author.

documentclass{memoir}

% usepackage{makeidx}% Emulated by memoir
makeindex

usepackage[columns=3]{idxlayout}

begin{document}

chapter{foo}

Some text.index{Alpha}index{Bravo}index{Charlie}index{Delta}index{Echo}index{Foxtrott}

printindex

end{document}