They're all different. C was a programming language developed in the early 70s which became incredibly popular, you wouldn't code in C today. Instead you'd go with one of the languages it influenced that built upon and improved it.
C++
This is one of the most popular languages in the world. Loads of videogames are programmed in this, as are Windows and Linux programs.
C# (C Sharp)
This is Microsoft's implementation of the C language. Only need to learn this if you'll be writing apps exclusively for Windows (more popular with newer systems I think, so Windows 8 and Windows Phone). Visual Basic .NET is probably more popular for developing Windows programs.
Objective C
Similar to C# but this is Apple's implementation of C. Learn this if you want to develop apps exclusively for Mac OS X and/or iOS. Note that you will need a Mac to code in this as it requires Xcode.
I don't like Java, but it's actually a good language to learn I think, it's very popular and if you're looking to develop Android apps then you're going to need it. In any school/college/uni that teaches any kind of programming, chances are you'll start out with Java. It's good for teaching the principals of learning to program.
For web related stuff, I started out with PHP, it was typically seen as an easy language to learn and you could be pretty lazy with it, due to this it got a bit of a bad reputation for being insecure. But in the last couple of years it's improved a lot and is more like a proper programming language now. If you're going to learn it, make sure any books or tutorials you're learning from are targeted to PHP 5 or 6. Preferably 5.3 or above as that's when it started improving substantially.
I did learn from a book myself but it's irrelevant now as PHP 4 was the latest version at the time. I read through it and it did all the exercises. While doing this I would also read tutorials online that taught me how to write scripts to do various things, explaining what the code is doing etc. so I found it fairly easy to modify and make it do what I want. It's pretty easy to find whole scripts people have put online. Sometimes I would download ones that interested me, or that did something I wanted to know how to do, and I would just look through the code to see how they did it. I just kinda learned like that really. Never had any formal teaching.
With Python I haven't actually done much yet, but if I actually put some time and effort in I could probably pick it up pretty quickly. I'd certainly recommend it. Again, plenty of tutorials online you could start with.
I don't really know of any good websites with tutorials for beginners to be honest. I would just search for "PHP tutorials for beginners" for example and check out the first page of links.