I find RealtyTrac to be useful for tracking Notice of Defaults, and using that info to surmise when and if there will be an auction/REO for that property of interest. If you are looking for auction info, it's a total crapshoot. Most of the time, you'll see auction info pop up after the auction has taken place. And for REOs, sometimes RealtyTrac gets the info after the REO has sold (assuming the property is priced well enough).
If you plan on doing enough investing, it may be worth it for the NODs, then send those to a realtor to check up on (assuming they don't mind doing all that extra work for you).