What it is: One of today's most popular content management and blog publishing applications online today. Used by 22% of the top 10 million websites, Wordpress's open-source aspect makes way for versatility; it can accommodate anything from small-time blogs to large fortune 500 companies.
Type: Open source
Pros: Wordpress is open sourced, making it very versatile. Wordpress has over 30,000 modules serving many different kinds of functions that tailor a website's specific needs.
Cons: Support and upgrades to the software usually are not included. One would have to be dependent on the open-source community to fix any bugs or install any updates.
More about WordPress here.