[tquai]

The Open DNS Resolver Project has a list of 25 million open resolvers. You can query their database for your IP address or up to a /24. Their site also has information on how to reduce or eliminate the problem via a couple options (RRL, BCP38). If you run a BIND resolver, consider switching to unbound. Part of this problem is rooted in BIND combining resolver and authoritative service in one daemon, which IMO "mis-educated" a lot of people.

http://openresolverproject.org/