The good guys at Hurricane Electric released an iPhone application that counts down to the IPv4 depletion. Download the iPhone appliaction along with other Ipv4 depletion related gadgets at http://ipv6.he.net/statistics/#iphone .
The application shows both IPv4 depletion data as well as some data about the global progress of moving to IPv6. The fact that they focus on the progress of IPv6 and not only on the depletion of IPv4 is good!
The application seems to be using Hustons calculations of days until depletion. I disagree with this number with about 7 months, but that is another story
It is unclear to me how they calculate the remaining IP addresses. As of today, their application claims that there are slightly less than 450 million IPv4 addresses.
If you summarize the 30 remaining A-blocks in the IANA pool you get 503 million. So this can not be how they calculated this.
If take the IANA pool and subtract the 5 blocks that are reserved (N=1 policy) you will get a total of 419 million addresses. Again, this can not be how they calculated this.
According to my estimates, the actual number of free IPv4 addresses (IANA pool + RIR pool) is around 800 million. See counter below (updated daily)