I'm a Java programmer and if there's one thing that I dislike about it, it would be speed. Java seems really slow, but a lot of the Python scriptsprograms I have written so far seem really fast. 
So I was just wondering if Python is faster than Java, or C# and how that compares to C/C++ (which I figure it'll be slower than)?
This totally depends on the usecase. For long running applications (like servers), Java has proven to be extremely fast - even faster than C. This is possible as the JVM might compile hot bytecode to machine code. While doing this, it may take fully advantage of each and every feature of the CPU. This typically isn't possible for C, at least as soon as you leave your laboratory environment: just assume distributing a dozen of optimized builds to your clients - that simply won't work.
But back to your question: it really depends. E.g. if startup time is an issue (which isn't an issue for a server application for instance) Java might not be the best choice. It may also depend on where your hot code areas are: If they are within native libraries with some Python code to simply glue them together, you will be able to get C like performance with Python as well.
Typically, scripting languages will tend to be slower though - at least most of the time.
How fast is Python?