yeah anything .Net related will earn you some cash .. C# would be worth a look with your C++ skills. As its an essential part of the .Net framework and basically java with a differenet name (ish)
AJAX will earn you some serious cash if you are good at it .. its used by the likes of google and MS a lot. And with Atlas MS have made it a lot easier to implement
http://www.asp.net/ajax/
python and perl are more generally used by ubber scripting people. Personally would not bother with sql as everyone and his brother that writes any kind of code knows a bit of sql as they use it to implement/call db commands etc so there's not not ££ in it on its own. And if you don't know much sql google is always your friend when it comes to getting by with sql commands etc . which is handy