Check out the nice work Jason over at MD5 Lookup is doing. This is a very similar concept to the one employed in LMCrack.

MD5 Lookup is an online lookup tool for doing MD5 hash to password lookups. The MD5 hashes are pre-computed and stored in a database. The cracking involves a search of the MD5 Lookup Database to return the associated plain-text password. Pretty neat.

The database has ~3,107,933,738 entries already and is being constantly added to.