eWeek recently ran a great article comparing various IT stacks. I'd been hoping they'd do something like it, as they had been briefly discussing various stacks and their denefits, but hadn't really done a major expose. I was impressed to see how .Net fared overall. In layman's terms, an IT stack is the group of core technologies that make up a web enabled product or process. A stack will include an operating system, a web server application, a database, and a scripting (programming) language.
Probably the two most well known stacks are the LAMP stack, and the .Net stack. LAMP is Linux, Apache, MySQL and PHP (or Perl or Python). .Net consists of Windows Server, IIS, Micrsoft SQL, and ASP. I like to think of it as the WIMA stack. As the article points out, there are a many other stacks, and an almost unlimited number of mutations.
At TACF, our public sites run off .Net stacks, but we have a few intranet sites running combinations. We have a WIMP stack, consisting of Windows, IIS, MySQL and PHP, and I think we have a WISP stack as well, replacing MySQL with Microsoft SQL. Open source is the bidniss. I like everything about it. I like the freedom, the customizeability, and the support from the community.