Until recently at work we've use Symfony1. It's going to end of life at the end of this year, and I think we're going to shy away from Symfony2 for now. It's a bit of a mess, I think, and it seems like they're going to correct a bunch of things in 2.1, but that won't be out for a few months. We'll probably reevaluate after that.
Our other goto framework is Cake. People do have a lot of good/bad things to say about Cake, but I rather like Cake 2. It's a little more mature now, and I don't really think it's as hugely complex as Symfony.
I use Zend on my own, but I'm becoming disillusioned with it. It seems to be overengineered and, after using Doctrine for as long as I have, its modeling leaves a lot to be desired.
Recently I've been researching FuelPHP (http://fuelphp.com/) and it seems to have potential. It's a little better designed than CodeIgniter and its ORM seems interesting.
Hope that helps.