Team Cymru is a pretty nifty site. I’ve found their IP-to-ASN mapping to be very helpful in the past, but just noticed that they also compile stats on malware, including a queryable malware hash database. It doesn’t aim to capture everything, but it looks like it could be a nice complement in identifying known badware.

For all of the amazingly helpful services they provide, they seem to keep a pretty low profile in the community.