May be this is overwhelmingly obvious to geeks, but I am going to describe it nonetheless. This might not significantly impress non-developers or the people and programmers (yes, they are different) who can't describe the word 'tooling'. A developer's productivity is highly dependent on the tools they use, whether it's a fancy big fat IDE platform or an editor as abstemious as VI.
Apparently, the business we work for doesn't really care for the tools we use most of the time - unless of course they are suppose to pay for it. But as simple as it is, If you know how the IDE you use works and how you can make it work the way you want, can make all the difference in your productivity. Here are some unimpressive hows:
1. Many mundane and stupefyingly boring tasks can be automated if your IDE supports macros or extensions. Learn it, it will relieve your back/wrist pain.
2. You may have some fun exploring a totally different software architecture than you may be writing day-to-day, this may turn out to be way too interesting than your day job. Learn it you will know how to design.
3. Sometimes your IDE is just used for a single purpose - coding, but If you know how to extend it you might be motivated to add some cool stuff to it like chat view next to problems view in Eclipse or may be rolling reddit RSS entries in status bar. Learn it, possibilities are never ending.
4. Integrate your IDE to reproduce bugs in your application. This is similar to 1 but different in the way it solves your problem, this may not always possible but worth a thought. I managed to write several plug ins for quickly reproducing bugs related to my application components. Learn it and you can quickly fix them.
5. You can devise custom metrics from your code like how many lines you delete everyday compared to how many you write. Learn it and you will get to know your weird programming habits.
6. You never know when you get in to alternative job market if you know your tools well. Tool developers are far less than application developers. So learn how your IDE works and you might end up earning more money than your own job pays.
All of these, among others I can't really word without beer, are from my own experience. Since Level 1 Human Programmer in 'M$-Land' I've been curious about the tools I use, right from Visual Studio Add-in to Eclipse plug-ins, it has been wonderfully interesting journey so far. Given a chance to speak and I would totally be interested in how Eclipse is architected and how Gel used to support extensions and how painful it used to be to debug Add-ins in Visual Studio 6.0. Boy, it is interesting!