LanCalculator from LanTricks is the program that everyone wishes he had during the CCNA exam. From a given IP address and subnet mask, LanCalculator will tell you the network IP address, the range of host IP addresses, the subnet broadcast address, and the amount of hosts allowed on the subnet. It will also convert addresses to binary.
The latest version of LanCalculator is 188.8.131.52 and does not appear to have been updated since June 2006.
Although the download page claims that LanCalculator works only with Windows 2000/XP/2003, it works fine on my Windows 7. However, LanCalculator does not support IPv6.