as a start read this :
http://en.wikipedia.org/wiki/Advanced_Encryption_Standard
http://en.wikipedia.org/wiki/Data_Encryption_Standard
the definitions are scary ones ! specially the word standard
i don't think someone from us will have the energy to write those brakers and make them work
at least not me ! Hope i am wrong
however check this cracker called deep crack written by the EFF (electronic frontier foundation)
http://en.wikipedia.org/wiki/Data_Encryption_Standard
i also saw this link on google search, but didn't visit the site.. too careful
www.freedownloadscenter.com/Best/free-crack-aes.html
i never tried to break those before.. so my help is limited
so I performed quick search