Best way to source foreclosure or pre-foreclosure opportunities?

[Raj A.]

In addition to working with an agent (and building a strong relationship with agents in general), are there any websites or services out there where an investor can get access to foreclosure or pre-foreclosure opportunities in a particular market? I've checked out websites like foreclosure.com but am unsure if that is the best website to use for this purpose. Also curious if Realtor.com or some other professional body has their own foreclosure service/website that I could subscribe to. 

Any pointers/guidance welcome. Thanks!