A tiny example wordlist is included with the cracklib package
itself. A very large dictionary suitable for use with cracklib
is also available from the cracklib sourceforge download page.
Other sources for word lists include:
Please note, the licenses on some of those word lists are
restrictive, so please read the licenses before redistributing them.
The cracklib-words distribution from the cracklib sourceforge
project page has been built solely from word lists previously
distributed with cracklib or crack packages and/or public
domain word lists.
For best results, supply cracklib with as large a wordlist as you
have available to you - blackhats brute forcing passwords have those
same lists, might as well use it to benefit your security.