Every phone at T-Mobile will be free on Saturday June 19th, starting at 8 a.m., for customers that switch to a family plan or add a line to an existing family plan. No phones are excluded, which means you could get the newest ones, like a myTouch 3G Slide or HTC HD2. (I'm in the middle of reviewing the Slide now and it's great for someone who wants all the Android coolness, but still wants a full physical keyboard. It's the best designed myTouch phone.)
I'm sure the best phones will go first, so better get there early if you plan on taking advantage of the sale. The release states "walk out of the store with a new phone for every new line with a two-year agreement.''
Father's Day is that Sunday, so it's a good way to get a last-minute gift if you need a new cellphone plan or if you want to switch your family to T-Mobile.
UPDATE: Radio Shack is doing the same thing on Saturday -- free phones with new two-year T-Mobile contracts.
According to the release from The Shack: "On top of a free phone, new customers will receive free activation in the form of a $35 account credit. Please note that add-a-lines and flex pay contract types are excluded from this offer."