What type of dev environment do you work in? Lately I've been doing a lot of my client-side testing in jsFiddle. It's easy to use and everything I need to see is all in one page, much handier than the text editor/browser method I've been using.
For my server-side work, I've stuck with XAMPP per Chris' suggestion several years ago.
What text editors do you use? I've been using Coda 2 and Espresso 2. They each have their own advantages. I've yet to find one that I will use exclusively, but I'm open to suggestions.
I've been pretty much living in Visual Studio with ReSharper for the past long while, since I use C# for nearly all my work. I use Notepad++ for python scripting, Espresso/WebStorm for anything web related.
I've been dabbling in Ruby a bit, and I got RubyMine for cheap a few months ago.
Text Editors (Linux): IDLE: Python vim: Everything
As for developing... I tend to push to a live server. That depends on what I'm doing. XAMPP on windows, MAMP Pro on Mac, on Linux I'll just scp all the files to my server and test there with Apache... Sumo I either start a remote deployment or run the entire system locally (~9GB of RAM)