I don't see what the point is in this poll. First, similar polls have been done recently, so this information already exists. Secondly, that's a fairly small (and seemingly arbitrary) subset of the available choices... Why not include, for example:

Pylons / Pyramid

Wicket

Groovy on Grails

Stripes

Lift

Compojure

Spring MVC

Snap

and any number of other popular frameworks?

All of that said, my primary choice is Groovy on Grails, so I voted "other."

I have abandoned server side frameworks all together, with the exception of a REST toolkit now days if you are building a web application the client side toolkits coupled with a REST service layer offer a much more robust development platform as well as provides a more usable and better performing end product.

But would you recommend that approach for a beginner, or is it better to start with a framework so you don't have to think of everything, and evolve your understanding?

How did you decide on your approach?

Yes I would because it is where the web is heading. I would adopt Dojo + jQuery or backbone + jQuery and a REST layer. I personally use JAX-RS because I do a lot of enterprise apps and Java is entrenched there, but there are REST libs for most major platforms now.

Other (Perl and Catalyst or Web::Simple, depending on the project).

Mostly Catalyst - http://www.catalystframework.org/

PSS + Vinegar

Just kidding, that's not a webapp framework, but if I wrote one, that's what I'd call it.

.NET Framework isn't a web framework. ASP.NET is the web framework that runs on .NET. Even then ASP.NET has two distinctly different options. ASP.NET MVC and ASP.NET Webforms.

...and ASP.NET Web Pages

I think Zend Framework should be on that list. That's what I use

Agreed. Very useful for PHP development.

On Ruby, Rails.

On PHP, Slim Framework http://www.slimframework.com/

Scala and Play. But really they are just a way to do some simple pages and provide a REST API

Other: Python Tornado

Noir! www.webnoir.org

I may be biased, though, since I wrote it :)

Zend Framework (1.x), and Symfony2

No Flex? (Does anyone use Flex?)

Pyramid

GluePHP/PropelORM/Savant3

you should add tornado

Isn't tornado something different?

Tornado (web.py)

Vaadin + Spring

erlang with cowboy and riak

Symfony

Cubic Web

Spring MVC

Lithium

Express

Flask

Flask is a type of Bottle :)