On a single computer you usually get 500 to 1000 keys per second, let's juice this up with a cluster.

First, you will need to split up your dictionary into segments. Let's take an example dictionary, wpa.txt, with 2,830,423 lines. With 64 cores, I will need 64 segments. 2830423 / 64 = 44225.

Code:
$ for file in `seq 1 64`; do head -n `echo "${file}*44225"|bc` ~/dict/wpa.txt | tail -n 44225 > ~/dict/wpa_seg/wpa_${file}.txt; done
This assumes your dictionary is in ~/dict/wpa.txt, and that you have a directory called wpa_seg to save the segments in.

Second, now that we have our segments we need to unleash the power of the cluster.

Code:
for file in `seq 1 64`; do (qrsh -now no "~/dict/aircrack-ng -w ~/dict/wpa_seg/wpa_${file}.txt -q -b 00:11:22:33:44:55 ~/dict/psl-02.cap > ~/dict/wpa_result/wpa_${file}.txt" &); done
This assumes you have your aircrack-ng binary in the ~/dict directory, that the bssid of the AP is 00:11:22:33:44:55, that you have psl-02.cap which has your handshake, and that you have a directory named wpa_result to store output. qrsh comes from a vanilla installation of the Rocks Clusters Linux distribution.

The power is great, I got a sustained test rate of 38,248 keys per second. Not bad for three minutes of setup.