How to search installed application based on functionality? My Applications folder has 486 entries, applications that have accumulated in the 30 years I'm using Apple hardware and software. Sometimes I'm looking for "that great application I have installed a few monts ago" but I am unable to remember its name, and I can spend a long time searching for it among hundreds of other apps.
Typical example: I installed Snagit during my last Parallels upgrade (it came as a bundle). It's a really great screen capture application, but how can I remember that "Snagit" is a screen capture application? As for its icon, it shows a white "S" on blue background, which isn't very helpful either.

On Unix there is apropos, but under Mac OSX this command only finds command line applications. 
Of course, there is the Web, but it is rather cumbersome to search the Web to find an application which is already on my harddisk. Not to mention the fact that some applications are hard to find even if you know exactly what they do.
Take for example OmniDiskSweeper, I doubt I will ever find it through the query "application that calculates the size of folders".
I thought of adding comments to applications, but I'm afraid they will disappear at the first update.

Is there an application that will combine the information found on the Web with all applications I have on my disk, and be able to answer queries based on keywords or on a description of the task I need? (for example "application, screen capture, installed in the last six months"). I.e., an intelligent Spotlight ("intelligent" in the sense of the semantic Web).

So here is my need: find an application that does a specific task in an overcrowded Applications folder, out of a few keywords or out of a sentence describing it.
You can use meta data. Select the app in Finder, press ⌘+i or secondary click -> Get Info.. There You have "Comments" section, where You can describe Your app (for example "great screen capture app"). Then You can search for an app in Spotlight using the keywords You privided. After upgrading the app, extended attributes are not erased.