Check out JustDropped(dot)com ...

This is probably a bit higher level than what you are looking for, but grabbing up expired domains is big business. Basically when a domain expires there is a grace period, and after that the first registrar that can make the request gets it. If you are waiting on a highly sought after address, you stand no chance using a standard web registrar. There are services specifically for "sniping" expired domains by having registrars repeatedly query ICANN around the time it is due to expire.

Like I said, its big business and probably not what you were looking for. But if you have deep pockets and have your eye on an expiring domain then it is something to look into.