TADS, by Michael Roberts, is an object-oriented IF lanugage with strong ties to the C programming language, and is my language of choice. It was originally shareware, but Michael Roberts has released it as freeware now. The package on most platforms includes a debugger and a program to turn platform-independent .gam files into run-time executables. This page merely gives the basic manuals and packages, along with some TADS modules for extending TADS' capabilities. There is a more comprehensive TADS web page available which covers many things I gloss over.
The latest incarnation of TADS is HTML TADS, which is just like TADS only with graphics and sound. HTML TADS doesn't have anything to do with browsers or the web; it uses HTML syntax to add graphics and sound.
Besides this page, I recommend you visit Brass Lantern for more information about interactive fiction.
You will also want to get the additional TADS release notes for versions 2.0.0 to 2.1.0, 2.1.1 to 2.2.2, and 2.2.3 to 2.4.0, as they have information not contained in the manuals. Also be sure to get the TADS Book of the Parser, which explains in detail how the parser works.
There are TADS programming packages for the following systems:
If you merely want to play TADS games, rather than write them, all you need is one of the following interpreters.
Let's say your system isn't in the above list. Never fear, the source is available, both for HTML TADS and regular TADS (as well as a Unix code distribution). In fact, if you want to run TADS under some variant of Unix, I recommend you download the source code and do a fresh compile.