WordPress

The old reliable that powers more of the web than you'd expect.

Best use cases
Blogs
Content sites
E-commerce
Business sites
Custom web applications
Pros
Huge ecosystem
Maximum flexibility
Open source
Mature platform
Endless plugins
Cons
Security maintenance required
Plugin conflicts
Performance varies
Can feel dated
Hosting complexity
Pricing
free
Free software + hosting/theme/plugin costs vary widely
Alternatives