if you want a specific domain (e.g example.com) then go to domaintools.com and look up the domain, if it says pending delete then plus 6 days to the update date, that will give you the drop date. or if it is avalible and you want to see if it had dropped then go to domaintools.com and look up the domain, in it will have some dots in the avalible box it it has dropped, if it has never been registered the box will be white. if you want all domains with "example" in it, then you need to cheack domain drop lists.
look in the whois domaintools.com provides extensive history as well, as well as records going years back... check it out if you really need to know something