Today (Thursday, Feburary 3, 2011) marks the day in internet history of when the internet finally ran out of space. The group responsible for assigning IP address announced that all possible IP addresses under the IPv4 protocol are now used up. So what do we do now that no one else can have internet under IPv4? We build more new internet!
The internet will slowly begin to shift towards IPv6 addresses which contain a lot more address than IPv4. Basically it works like this:
Your current IP address is 4 hexidecimal numbers represented in the base 10 system. These four numbers range from 0 to 255 (the range of 2 digits in hexidecimal format).
The new system increases each of these four numbers to the range of 4 digits in hexadecimal format (meaning that the range goes from 0 to 65535 (read: A LOT of possible combinations for IP addresses).
So enjoy your last few days of having your old IP address as soon you will be transitioned to a new system with a new address.
All major OS systems support IPv6 (Windows NT*, Macintosh 10.x, Most Linux Distributions). Your ISPs will do all the work of reassigning behind the scenes and you won't notice a thing.
*Windows NT refers to all Windows OSes that use the NT Kernel (earliest being 2000)