In fact, a lot of fun programming is done in C -- for instance, system software and data managers such as Berkeley DB. If you want to be able to do more than write a simple web app, C is a great language. If you want to write a great, fast game, C is again a great choice. You can write an entire OS in C.
Why learn C ?
C is often considered to be the mother of all languages because so many other languages have been based on it.
Though C is simple it is one of the most powerful languages ever created. Considering it was created over 40 years ago, it is still used heavily and is usually in the top 5 or 10 most popular and most widely programming languages in the world.
Learning C can actually make you a better programming in other languages like C++, Java, or C# by equipping you with a mental model of what the computer is actually doing when you run your programs.
By learning how things really work "under the hood", and understand memory space, CPU architecture and so on, you can create more efficient programs, and obtain a huge advantage over other programmers in the process.
If you want to become a better developer, learning C is a great way to start!