I've been waiting for a particular domain name to become available. The current ownership expires today?

does this mean I can purchase it if the current owner doesn't renew? If so how quickly and where do I go to find it?

No. Odds are that you won't be able to get it. You can go to www.godaddy.com and "backorder" it but all that does is establish your bid price for when the domain name goes to auction. There is also a "buy" service that will try to negotiate a deal for you. Good Luck!

No you can't buy it. The domain registrar places a lock on the domain (not sure how long). I think it's typically a year, because an expired domain I wanted to buy back is currently locked for a year.

After a domain name expires, you will have to wait a month for it propagate out of the nameserver for you to get it.

You can also check out http://www.godaddy.com and see if you can pre-register it still.