Check out Eclipse, its a great cross-platform IDE, some people don't like its speed as it is in Java, but it gets the job done.<p>Though YMMV depending on what you code in. Some IDEs are better suited for certain languages than others.<p>Best to start with a comparison page (link below) then google/ask questions once you get a list of what looks good.<p><a href="http://en.wikipedia.org/wiki/Comparison_of_integrated_development_environments" rel="nofollow">http://en.wikipedia.org/wiki/Comparison_of_integrated_develo...</a>
We'd do better if you told us which languages you plan to work on. For instance, IntelliJ Idea, community edition, is a pretty strong contender, but it's at its best in JVM languages.
Personally I'd only bother with an IDE for Java, Objective-C or C# - then I'd choose IntelliJ, Xcode and Visual Studio respectively.<p>I'd stick to a text editor otherwise.