Katie, You can try foreclouser.com they provide a free trial period and it is $ 30.00 a month after that. I have used many different sites and this one seems to have a better base of information.. Suffolk county has a tax sale in the Fall the list of properties comes out aroud Sept. and the auction is in Oct.-Nov.
I know that the listing services for Long Island is indicating the status of properties listed. As an agent I have access to this information and could provide FREE account at nzappola@listingbook.com if you have any property in question or that you would like access to I would be happy to work with you.
If you have trouble opening an account contact me Nunzio.Zappola@elliman.com

For both Suffolk and Nassau counties, suggest that you contact the respective financial departments for getting that type of tax foreclosure information I would think that any information provided would be free or nominal (cost) at best.

You Can't! Deal with a good agent who can get you what you are looking for.