Bioinformatics - DNA binding, sequence-specific protein data
You are seeking a database of transcription factor binding specificities. Some model organism databases (which are manually curated), such as Wormbase contain some of this annotation. I suggest you search PubMed for papers by Tim Hughes at the University of Toronto. He has published extensively on this topic over the past 5 years.  Papers he cites, and papers that cite him, will let you bootstrap your way in to the topic.