Vanilla markItUp! for Rails 3.x, works with ERB, so, no extra gems needed like SCSS (huh?) or LESS. It comes with these sets from markItUp!: Html, Textile, Wiki Syntax, Markdown, and BBcode, if you use one of them maybe you will need to add other gems to parse it ;-).

Markitup with Bootstrap styling for rails3.

Syntax highlighted markdown editor for rails

An engine that enable you to mark any ActiveRecord model as many as you like

Unobtrustively control markup rendering of ActiveRecord object attributes

Markup support for rails/active record.

Save marshaled objects using ActiveRecord

As I said in the summary

Mascot rails integration.

The ruby agent reports API traffic to http://apianalytics.com

Useful Rails Patterns Generators

A maskable attribute is an attribute that is made up of other attributes (masks), this ordering is set in the masked attribute and preserved across updates.

Mask out your controller logic with mock data to make building views easier.

Adds methods for a bit masked field

A multi-tenant OpenID Connect and OAuth 2.0 provider with a signing key per tenant, SAML, SCIM, passkeys, and a management API. Mount it at the root of an app of its own, or inside an existing Rails app.

Masq2 supports OpenID 2.0 and supports SReg, AX (fetch and store requests) and PAPE as well as some custom additions like multi-factor authentication using a yubikey

Massdebator api gem. Connect to the massdebator API and create and manage debates for your organization

Tools for specific company tasks

A Ruby on Rails library to help with mass database operations like insert, update, save, validations, etc (much faster than typical ActiveRecord Interactions

This gem gives a developer a set of tools for securing access to their endpoints.