http://www.icce.rug.nl/docs/cplusplus/
I like the above site a lot. Especially for someone trying to make a
transition from C to C++, it is quite nice.
Another nice site is
http://users.ece.utexas.edu/~adnan/C++/
Both these are ad-free sites, with just pure good quality free
content. I am thankful to the authors of the documents.
BUT, as others have pointed out: one has to practice a lot. I am
trying to make a transition from "C with classes" to C++. It is
gradual, but to begin with these are some things I try to do: use STL
when possible, use references, learn to use const when possible, try
to avoid pointer arithmetic, use the library facilities when you can
rather than reinventing the wheel (that is not quite circular) ...
Sometimes my first version of a program looks a lot like C (and a bit
dirty, although this is not to say C is dirty), but then I make an
effort to clean it up, and simplify it, and often I notice that using
some C++ features, I can simplify the code, make it more readable,
safer, ... I am no expert, so I welcome some experts to comment on
what I have suggested above.