I thought one could get an alert set up for when a domain name becomes available. Where can I find that?

If it exists, I'd like to know where it is found.

More precisely, I'm looking after a domain name that is set to expire soon and want to make sure I will be the first to register it.

Network solutions offer a service called snapnames.com which allows you to camp on a domain and take part in an auction of multiple people are wainting for the same name to become free. There is a moderate charge plus a percentage of the bid.