Where to start - that's a question with too many answers.
If you are looking to get a full-time job as a programmer, you'll be better off learning one of the more popular languages - that being C++, Java or C# (IMO). Of those, I would recommend Java - it is easier to learn than C++ and there is a lot of good help content on the Sun website.
If you're just looking to mess about making projects in your spare time. You really need to decide what you want to do and then decide the best language for the job. Want to write mobile phone games? Learn Java. Want to crack software? Learn C and assembler. Want to write server-side webpage code? Learn Python or PHP. The list goes on and on.
If I was pushed to recommened one language, I would go for Java.