C#/ASP.NET specialists are pretty well paid. Microsoft has a lot of architectural pieces you can plug together for extremely scalable solutions. Remoting servers for your application tier give you a TON of cheap scaling. Clustered and federated SQL Servers give you a beefy backend when you eventually need it. Decent amount of freelance/independent work here, if you're patient and know where to look. Also Windows Mobile still stands a fighting chance as a leading mobile platform, at least in the enterprise world.
Java is kind of like .NET, only, at least in markets I'm familiar with, it's fading. Sure, it can scale to no end, but it has a pretty high TCO. Unless you're going into financial programming, I'd leave Java aside. Knowing C# gives you an entree into Java should you ever need it.
Ruby, RoR is up and coming, but not, from what I've seen, highly well paid.
PHP is often underpaid, but has potential. Being pretty mature, there are a lot of roles out there. It _can_ scale -- Yahoo! proves this -- but not exactly out-of-the-box. Lots of freelance work available here.
Erlang has a lot of value, and I suspect will continue to grow in this world of multi cores and multi processors. Concurrency is soon to be king.
Python is a good utility language, but unless you're a Python guru, you probably aren't getting paid squat to know it.
It's always good to know C/C++. Heck, it's good to know Assembler insert platform here to boot. Excellent fundamentals, if not a lot of LOB work around these days. C++ is good for mobile work. I bet Android increases the amount of mobile work here as well.
Knowing Obj-C/Cocoa is growing in value as well. Even with low market penetration, your potential audience is pretty upmarket. Room for high margins here.
Lisp, Perl, eh, not bad to know, especially Lisp for fundamentals. For that matter, Smalltalk has value as well. Smalltalk even has a web framework these days ...
If you want to be highly employable, I'd suggest some combination of C#, Ruby, PHP, Python.
Java is kind of like .NET, only, at least in markets I'm familiar with, it's fading. Sure, it can scale to no end, but it has a pretty high TCO. Unless you're going into financial programming, I'd leave Java aside. Knowing C# gives you an entree into Java should you ever need it.
Ruby, RoR is up and coming, but not, from what I've seen, highly well paid.
PHP is often underpaid, but has potential. Being pretty mature, there are a lot of roles out there. It _can_ scale -- Yahoo! proves this -- but not exactly out-of-the-box. Lots of freelance work available here.
Erlang has a lot of value, and I suspect will continue to grow in this world of multi cores and multi processors. Concurrency is soon to be king.
Python is a good utility language, but unless you're a Python guru, you probably aren't getting paid squat to know it.
It's always good to know C/C++. Heck, it's good to know Assembler insert platform here to boot. Excellent fundamentals, if not a lot of LOB work around these days. C++ is good for mobile work. I bet Android increases the amount of mobile work here as well.
Knowing Obj-C/Cocoa is growing in value as well. Even with low market penetration, your potential audience is pretty upmarket. Room for high margins here.
Lisp, Perl, eh, not bad to know, especially Lisp for fundamentals. For that matter, Smalltalk has value as well. Smalltalk even has a web framework these days ...
If you want to be highly employable, I'd suggest some combination of C#, Ruby, PHP, Python.