Borland has several compilers free for download.
These include the 5.5 version of their C++ compiler (one of the best around!) as well as a number of old versions of their C++, C and Pascal systems.
http://www.borland.com/products/down..._cbuilder.html (choose "compiler").
http://bdn.borland.com/museum/
free registration required for both. Borland doesn't send anything you don't give permission for.

Microsoft has a free version of their C++ compiler for .NET (the very latest version) also available on their website.
Search microsoft.com for VCToolkitSetup.exe

Java can be freely downloaded from http://java.sun.com (for PC, for Mac contact Apple).

Python works on just about everything too, http://www.python.org

Apart from those all you really need is a good editor. I am somewhat partial to VIM (http://www.vim.org) and Eclipse (http://www.eclipse.org).

There's tons more but this should keep you occupied for a few years