You should learn a new programming language!
Learning a new programming language is great for two reasons:
1. It expands your mind. Your brain gets exercise when it’s forced to think in new ways.
2. If you’re building something big, take the time to learn the best tool for the problem at hand.
I learned this the hard way when building Zyked.com. At the time, ASP (the old one, not .NET) was all I knew. I spent almost a year slowly building a large site, before hitting a wall when I came to AJAX stuff and Facebook integration. I then learned Ruby on Rails and rebuilt the site in 1/10th of the original time.
Learning to be productive in a new language, framework, or tool rarely takes more than two weeks. It’s worth it.
Functional languages are hyped right now because they scale better across multiple processors.