Microsoft uses methods other than service packs for many IIS updates. Here are a few sites you can check for updates

MDAC
For the latest information about Microsoft Data Access Components (MDAC) and important downloads, go to http://www.microsoft.com/data/download.htm. On this page, you can find a tool to help you determine the version you currently have.

Microsoft FrontPage 2000 Server Extensions
The server extensions contain a few important security-related fixes. You can find updates to the server extensions at http://msdn.microsoft.com/workshop/c-frame.htm#/workshop/languages/fp/default.asp. At the time of publication, the most recent update was version 1.2, which Microsoft released in November 2000.

Scripting Engine Updates
You can find updates to the Windows Script (WS) engine at http://www.microsoft.com/msdownload/vbscript/scripting.asp. From this site you can update VBScript, JScript, and Windows Script Host (WSH). Because Active Server Pages (ASP) lets users incorporate VBScript and JScript into ASP files, updating the scripting engine gives you the benefits of new features and fixes.