Sinatra like

These frameworks offer rich configuration and are less opinionated than Rails-like or full-stack.

http://expressjs.com

Express.js is probably the most popular robust and mature framework

http://spumko.github.io

Hapi is a variation of Express.js build on top of it by WalmartLabs.

Just REST API

For those who use rich-client/front-end MVC frameworks (or not) and just need to spin up a fast Node.js REST API server.

http://mcavage.github.io/node-restify
https://github.com/flatiron/restful
https://github.com/keithnlarsen/restmvc.js

Ruby on Rails like

http://compoundjs.com/ (former railswayjs)
http://railwayjs.com/
http://geddyjs.org/

Full-stack

That’s where Node.js really shine. The full-stack MVC frameworks are bundled with scaffolding, template engines, websocket and persistence libraries to allow you build real-time scalable web apps.

http://derbyjs.com
http://towerjs.org
http://balderdashy.github.io/sails
http://meteor.com

Meteor is more of a platform with its own packages and services. Its very opinionated and has a steep learning curve.

Others

http://flatironjs.org
https://github.com/isaacs/npm-www
http://frisbyjs.com
https://github.com/robtweed/ewdGateway2

Middleware

http://www.senchalabs.org/connect

Static Site Generators

https://github.com/jnordberg/wintersmith
http://docpad.org
http://blacksmith.jit.su
https://github.com/felixge/node-romulus
https://github.com/caolan/petrify