While md5 is a fairly strong hashing algorithm, even with the best algorithm weak passwords based on dictionary words and/or their variants can be easily compromised. There are a few sites on the net that have built searchable databases of "weak" password allowing quick strength checks of md5 hashes. But, each one of those databases has different set of hashes and a different database size, making a "complete" search rather difficult. So, I've come up with a little aggregator script that gathers information from 5 different (tell me if you know of others) sources and offers the resolved data on a single page, thus giving you a fast response from a cumulative database.
The script can be downloaded from here,
http://ilia.ws/uploads/hash.php.txt
It is released under BSD license, so anyone is free to use it.
hwblog - Ho Wang on : PHP MD5 Cracker/Dictionary Attacker