Book the date, November 24, as the day the cell phone providers are required to provide existing cell phone consumers the ability to switch phone numbers between companies and plans. The cell phone companies have been fighting to block this move because they claim it will cost them more money, but truthfully it's going to be great for cell phone users. Now, customers who have been using on provider and stuck with one plan because they could not lose their current cell phone number will have the ability to get a cheaper rate with another provider. This will force cellular companies to compete, lower prices and increase cellular reception areas. Those carriers who provide the best service will win.

Source: Cellphone Carriers.com
I'm VERY excited about this because I am planning to switch from Sprint to T-Mobile when the Treo 600 comes out and I want to keep my old number. I'm just wondering if I can transfer my existing number without having to wait until Nov. 24th.