Modules
HtmlSanitizeEx can be used to sanitize potentially malicious user input.
Allows basic HTML tags to support user input for writing relatively plain text but allowing headings, links, bold, and so on.
Scrub CSS.
Allows all HTML5 tags to support user input.
Allows basic HTML tags to support user input for writing relatively plain text with Markdown (GitHub flavoured Markdown supported).
This module contains some meta-programming magic to define your own rules for scrubbers.
Scrubs neither tags, nor their attributes.
Strips all tags (and, naturally, attributes).