Nowadays, so many applications are moving from the traditional desktop GUI to a web- or browser- based GUI. I’ll list a few here from PHP alone:
phpMyAdmin, which is a complete MySQL admin Tool which is accessed from a browser,
webcalendar, which is a group or single-user calendar which also gives reminders,
Gallery, which is a photo-gallery application, but whose configuration and setup surpasses in complexity most desktop applications, because of the number of options it offers, and,
xoops and php-nuke which are robust content management systems,
again, whose users need to handle so many forms and menus for setup.
Extending the idea logically, one feels that the only places that web-gui based apps will not go is listening to system messages and such other internals software (look at sysinternals). But with the windows API accessible in several web-scripting languages now, it is only a matter of time before you get a process spy or a network admin tool in web-based packing.
Closely related to this is the development of xml-based databases like xindice and xmldb. Though now these do not replace any databases in any way, it is not impossible to add enough complexity to them to make them robust for purposes of storing complex real-time data as well.
Then we have web-services and a pay-per-use software-component architecture, examples of which are Paypal.
The web is doing a lot more now!