Want to expand on my marketability as a web developer. What language should I learn?

I’ve been developing in PHP for about 7 years now and while I still learn new methods and techniques, I think it’s a great time to take my knowledge that I’ve gained and port it over to a new language. The problem is that there are so many out there. I just want to expand my horizons and increase my value in the web development market.

Some I’m considering are Ruby, Python, ASP or Coldfusion. I’ve been getting a lot of referrals for CF work and it seems like an interesting enough language to learn. I’ve also been getting a lot of questions from high-profile potential clients asking if I do ASP work.

I understand from other ASP developers out there that they can pretty much name their price because the demand for skilled coders in this language is so high right now.

Ruby is great and I know i can pick up on it with relative ease considering pretty much all my code nowadays strictly adheres to object oriented coding practices, but the interest in the language seems to be fizzling out. Plus, I heard it isn’t that great for high-volume websites and it doesn’t scale well. I need some verification on that, though. Should probably do a bit of research.

I don’t see any demand for Python developers as it seems like more of a niche market. Though, it seems like a fun language to learn in your spare time.

Just want to be able to meet the demand in the current job market and diversify my skill set.

Comments, thoughts? Thanks!