I know C# and VB and want to learn a new language soon, but I don't want to learn something which is 'just like C# or VB but a bit different'. Ruling out Java for example (I already know a bit anyway).
What's a good language to try? Should I go for an interpreted language like python, ruby, or PHP, or will I learn more from a lower-level language like C? Will C be too 'heavy' for evening learning?
Whatever your suggestion, could you link to a good resource or two?
I don't really have a purpose for learning a new language, so good mini-project ideas would also be welcome!