Is there a position within your company that you'd like to be in (some other team doing more exciting work, etc)? If so, try to figure out what it'd take to move there. If not, get a new job.

But before doing that, do the following (which you should be doing anyway):

* learn about new things in your / neighbouring fields that interest you - this is a career where you want to be learning all the time, and much of the learning will be on your own time/dime (the upshot is that you don't need to slog thhrough new things - breadth is more important than depth)

* keep an eye on the potential new jobs (interesting new jobs or companies), maybe apply to a few places to see how far you go

* increase your visibility; blog, relevant activity on hn/reddit/stackoverflow/quora/..., source code examples or open source contributions, community involvement (organising / speaking on events), screencasting your coding sessions - whatever sounds more fun to you

Doing these three will help make you more valuable (and more clearly valuable) to the company so that you might have an easier time of convincing your manager(s) to give you more challenges/responsibility, and if that fails, you'll be in much better position when looking for a new job.