My thoughts on IDE’s:

1. Eclipse: (Windows/Mac/Linux)
The latest version available is the indigo release. It provides set – infact a lot of tools for developing in a multitude of languages from java, php, python, mobile apps – it has tools for the data modeling, reporting – all most everything you will want for.
As I write this, my personal favourite is Eclipse – helios release, all the releases bring new features, but some are just an extravagance for the ordinary developer.
2. Netbeans,(Windows/Mac/Linux)
Primarily came into as a java development environment, it is still hot among various segments of developers. It is lightweight and its modular structure allows to create modules and incorporate. Apart from java, j2EE app development it supports PHP, python, c, c++ , mobile.
3. Aptana: (Windows/Mac/Linux)
Basically based on the eclipse platform, aptana has emerged as foremost used IDE for web development, with the support of ruby (radrails), it supports javascript code assist, css, html code assist, debuggers. I feel aptana with it rad rails flavour is mostly acclaimed among the ruby folks.
Also aptana has found its way to be nice web designer toolkit.
4. Syntori (Mac)
Basically for java developers, it includes various features for debugging.
5. Code::Blocks (Windows/Mac/Linux)
This is c, C++ ide, it is build around plug-in architecture, so it can extended by installing/creating new plugins