Better Compass integration for Sinatra (part of BigBand).

Sinatra Conditions gives you the ability to use additional conditions.

Small Sinatra extension to add a content_for helper similar to Rails'

Adds controllers to Sinatra

Rack middleware to disable cookies when static content is being served, which can prevent caching on some HTTP accelerators (Varnish).

Create documentation for an API built in Sinatra.

A Sinatra Extension that makes working with CSS easy.

Cycle through pages at a regular interval

Cache extension on Sinatra

helper.

A quick and simple way to set defaults for the params helper on a per route basis.

Saves you from having to write routes just to render templates with the same name. Rails-style.

Sinatra can be aynchronous and provide WebSockets using Thin and Skinny.

Drop in disqus to any Sinatra view via a handy helper.

Sinatra Extension for working with DataMapper (another Sinatra-Sequel Rip-off)

Tools for creating a simple web API

A user authentication middleware built with Sinatra and Warden

Provide autoloading of Model classes and Controller for sinatra to allow for simpler writing of MVC web applications.

Define your params schema with the strong library dry-schema.

A simple CMS extension for sinatra