Catched.com is one place.
However, many .xyz don't get picked up on the drop by a service because few investors or end users want to buy .xyz domain names. You can hand reg some decent .xyz domain names after they drop without paying a premium price for a drop catching service.
Also, note that Catched.com will not catch any .xyz that are premium domains by the registry. If they do end up catching one for you, they will not deliver it to you because of the premium charge by the registry. Best to wait after the drop and just hand reg it at the premium price, if you are so inclined.