Create a smart folder, alt/option-apple n. For the criteria, under Any, change it to application. Then for Kind, click on Comment (for example) is ... your word(s) (I use dockapp which is unique enough).
For the apps you want, do a show info, Apple i, and type dockapp (or whatever you choose) in the Spotlight comment (I'm assuming your using Tiger, yes?) Hit save and put that folder in your dock and wherever you want it.
This also works great for documents, images, whatever. And it will update itself once you add or remove the comment (or whatever criteria you set).
By doing this, you can also use spotlight to search and open the app by calling up dockapp. That way you don't even need a folder in the dock.