This Brute Force Calculator determines the amount of time it would take to exhaust the keyspace of a particular password given the complexity of the password and the number of keys per second that can be cracked. The keys per second depends on power of the system cracking the password and the algorithm the password is encrypted with. It should be noted that this calculator does not speak to the to the choices users make when choosing passwords. Additionally, for certain algorithms, there are well known methods (e.g. rainbow tables) which greatly reduce the amount of time it takes to exhaust a keyspace. Before relying on these results, its recommended that you attempt to identify if speeder methods exist for the algorithm your targeting. freerainbowtables.com is a good start.
For convienence, a list of popular algorithms along with the number of keys per second has been provided. This list was generated on an 3.4GHz Intel Core i7-2600K, using benchmarks from john the ripper and aircrack-ng (for WPA-PSK). Since computation times varies across systems, the "custom" option is available to allow more realistic results applicable to your environment and the current state of cracking.
john's benchmarking output