Simple Machines Forum - Simple Machines offers free open source software such as SMF, the powerful and easy to use community forum written in PHP. Start interesting discussions on your website!

Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.

Raddle - A web-based forum where users submit links, pictures, posts, etc.

Influitive - Influitive helps companies increase customer lifetime value and accelerate sales with the power of their own customer advocates. Inspire your customers to stay longer, share their experiences, and attract new business.

Invision Community - Invision Community is a flexible, integrated set of apps for building communities on the web.

Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.