The following applications use wxWidgets, which is a thin wrapper like SWT.

• Dropbox: the hot new kid in the online storage market
• filezilla (used to use MFC and Windows only)
• MadEdit
• JD-GUI: a Java decompiler
• Audacity
• xCHM

According to this post and the official Qt In Use page, these applications use Qt:

• Opera
• Google Earth
• Skype
• Photoshop Elements
• KDE, Qtopia, OPIE
• Mathematica
• VLC media player

In addition, these applications use Qt as well:

• Psi
• calibre

In the Java world, we have two choices: Swing and SWT. Swing is light weight; it does its own painting, so it’s easy to change a Swing application’s look and feel, but it may not look native. While SWT is heavy weight: it’s a thin wrapper around OS widgets, so an SWT application looks native to its underlying OS platform. SWT cannot be used in Java applets because of this, but not many people care about applets anyway.

These applications use Swing:

• MagicDraw (uses JIDE)
• DbVisualizer (uses JIDE)
• IntelliJ IDEA
• NetBeans IDE
• FreeMind
• Yong Zhong Office suite

These applications use SWT:

• Azureus: the popular BT client

I’ll update the list when new information becomes available. I’m interested in finding out what’s being used in Google (such as Chrome) and Mozilla (Firefox and Thunderbird).