Brutus

This Windows-only cracker bangs against network services of remote systems trying to guess passwords by using a dictionary and permutations thereof. It supports HTTP, POP3, FTP, SMB, TELNET, IMAP, NNTP, and more. No source code is available. UNIX users should take a look at THC Hydra.

Wfuzz

Wfuzz is a tool for bruteforcing Web Applications, it can be used for finding resources not linked (directories, servlets, scripts, etc), bruteforcing GET and POST parameters for different kinds of injections (SQL, XSS, LDAP, etc.), bruteforcing form parameters (user/password), fuzzing, and more.

RainbowCrack

The RainbowCrack tool is a hash cracker that makes use of a large-scale time-memory trade-off. A traditional brute force cracker tries all possible plaintexts one by one, which can be time consuming for complex passwords. RainbowCrack uses a time-memory trade-off to do all the cracking-time computation in advance and store the results in so-called "rainbow tables". It does take a long time to precompute the tables but RainbowCrack can be hundreds of times faster than a brute force cracker once the precomputation is finished.

SolarWinds

SolarWinds has created and sells dozens of special-purpose tools targeted at systems administrators. Security-related tools include many network discovery scanners, an SNMP brute-force cracker, router password decryption, a TCP connection reset program, one of the fastest and easiest router config download/upload applications available and more.

L0phtCrack

L0phtCrack attempts to crack Windows passwords from hashes which it can obtain (given proper access) from stand-alone Windows workstations, networked servers, primary domain controllers, or Active Directory. In some cases it can sniff the hashes off the wire. It also has numerous methods of generating password guesses (dictionary, brute force, etc). LC5 was discontinued by Symantec in 2006, then re-acquired by the original L0pht guys and reborn as LC6 in 2009. For free alternatives, consider ophcrack, Cain and Abel, or John the Ripper.

Medusa

Medusa is intended to be a speedy, massively parallel, modular, login brute-forcer. It supports many protocols: AFP, CVS, FTP, HTTP, IMAP, rlogin, SSH, Subversion, and VNC to name a few.

PwDump 6

Pwdump 6 is able to extract NTLM and LanMan hashes from a Windows target, regardless of whether Syskey is enabled. It is also capable of displaying password histories if they are available. It outputs the data in L0phtcrack-compatible form, and can write to an output file.

RainbowCrack

RainbowCrack is a general propose implementation of Philippe Oechslin's faster time-memory trade-off technique. It crack hashes with rainbow tables. A brute force hash cracker generate all possible plaintexts and compute the corresponding hashes on the fly, then compare the hashes with the hash to be cracked. Once a match is found, the plaintext is found. If all possible plaintexts are tested and no match is found, the plaintext is not found. With this type of hash cracking, all intermediate computation results are discarded.

Brutus

Brutus is one of the fastest, most flexible remote password crackers you can get your hands on - it's also free. It is available for Windows 9x, NT and 2000. Development continues so new releases will be available in the near future.

AirSnort

AirSnort is a wireless LAN (WLAN) tool which recovers encryption keys. AirSnort operates by passively monitoring transmissions, computing the encryption key when enough packets have been gathered.

THC Hydra

THC Hydra is very fast network logon cracker which support many different services.

John the Ripper

John the Ripper is a fast password cracker, currently available for many flavors of Unix, Windows, DOS, BeOS, and OpenVMS. Its primary purpose is to detect weak Unix passwords. Besides several crypt(3) password hash types most commonly found on various Unix systems, supported out of the box are Windows LM hashes, plus lots of other hashes and ciphers in the community-enhanced version.

Cain and Abel

Cain & Abel is a password recovery tool for Microsoft Operating Systems. It allows easy recovery of various kind of passwords by sniffing the network, cracking encrypted passwords using Dictionary, Brute-Force and Cryptanalysis attacks, recording VoIP conversations, decoding scrambled passwords, recovering wireless network keys, revealing password boxes, uncovering cached passwords and analyzing routing protocols. The program does not exploit any software vulnerabilities or bugs that could not be fixed with little effort. It covers some security aspects/weakness present in protocol's standards, authentication methods and caching mechanisms; its main purpose is the simplified recovery of passwords and credentials from various sources, however it also ships some "non standard" utilities for Microsoft Windows users.

Aircrack

Aircrack is an 802.11 WEP and WPA-PSK keys cracking program that can recover keys once enough data packets have been captured. It implements the standard FMS attack along with some optimizations like KoreK attacks, as well as the all-new PTW attack, thus making the attack much faster compared to other WEP cracking tools.

Ophcrack

Ophcrack is a free Windows password cracker based on rainbow tables. It is a very efficient implementation of rainbow tables done by the inventors of the method. It comes with a Graphical User Interface and runs on multiple platforms.