The information presented here is by no means complete nor is it organized. I just wanted to present some perspective on the component software as to spur enough interest for reader to look futher into this issue.

VBX

As noted by the famous Byte article ( May 1994 / Cover Story / Componentware ) one of the first widely known uses of component technology was VBX, or Visual Basic Controls (eXtensions?).

Plug-In Technologies

Many applications are using the plug-in technology to allow 3-rd party developers to expand on the application's functionality. It started with import-export file format filters and developed in some cases into full-blown component architectures. Among the first mainstream applications using plug-ins was Adobe Photoshop. Another widely known example is Netscape Navigator/Communicator with hundreds of plug-ins that support various data formats. One may want to note Illustrator, PageMaker, Premier, Acrobat from Adobe; QuarkXPress; Freehand,  Director, X-Res from Macromedia; CorelDraw, CorelPaint from Corel.

SOM

SOM by IBM is a veteran componentware product. By reading the IBM article on SOM (IBM's System Object Model (SOM): Making Reuse a Reality) one can't help but note many similarities between rationales of COM and SOM. Purists would ask, who was the first ?(IBM was), pragmatics would ask, who makes money out of it (you bet the answer is Microsoft, but it is a wrong answer, no one actually does).

OpenDoc

An artifact of Apple's vision on the component software (Apple DU: ICS: Component Technologies), an OpenDoc is a great example of how a well-designed and carefully implemented software system could go into maturity and be buried by mismanagement, lack of marketing focus, or maybe just mere insufficient funding.

CORBA

A major player in the component software field, the CORBA effort is undertaken by the Object Management Group. Use this link: What IS CORBA????  to satisfy your curiosity about the abbreviature. Comparing ActiveX and CORBA/IIOP is biased, of course, but worth reading anyway. There are many high-end products based on the CORBA technology. Looks like there is enough "beef" in CORBA to spur the interest of serious people. One of the patterns authorities, Douglas Schmidt quotes CORBA as one of his research interests.

JavaBeans

JavaBeans is a recent entry into the world of component software. It may finally deliver on the promise its precedors made. Barely a year-old, JavaBeans is already supported by virtually all development tool vendors and by most major Java developers. A walking tour of JavaBeans - JavaWorld - August 1997 is a good overview on the technology.

JavaBeans is often considered a competitor to ActiveX (like in JavaBeans Takes On ActiveX). In a bright move to encourage its supporters, JavaSoft has demonstrated interoperability between JavaBeans and ActiveX. Lotus has futher pushed the JavaBeans technology and came up with the InfoBus technology (JavaBeans "InfoBus" Draft Specification) which promises seamless integration between data processing components (yawn).

ActiveX and Security

Speaking about ActiveX one cannot help noticing the ActiveX security bugs scandal
which spurred a lot of public discontent and flames.

Pointers

Enquiring minds can find a lot of information on component technologies on the Internet. Take for example a Component-Oriented Programming page created by Guy Laden guy@math.tau.ac.il.