I think you should start at expireddomains.net. Create a free account and you can search for all the dropped domains based on TLD's . Use the filter option (Show filter to select the dropped domains in last 12 or 24 hours) and search for the domains. Please note that different TLDS drop at different times. Need to keep a watch and do your search.
You can also use dropcatch.com to catch a domain but you will need to pay a premium and also if multiple people are interested in the domain, it goes for auction.
Anyway, use your favourite registrar for buying once you have searched for the domain.