One of the best suite of tools available for free for security professionals with a wide range of tools categorised as per requirements
Some of these categories include Information gathering, vulnerability analysis, wireless attacks and web applications to name a few.
Kali Linux contains a large amount of penetration testing tools from various different niches of the security and forensics fields.
These tools can be found here – Kali Linux Tools
Kali Linux is an open source project that is maintained and funded by Offensive Security, a provider of world-class information security training and penetration testing services. In addition to Kali Linux, Offensive Security also maintains the Exploit Database and the free online course, Metasploit Unleashed.
Regular tutorials and security news are frequently updated on the Kali linux blog. The link to the blog can be found here