The above said keyboard search engine, KeyXL allows you to search keyboard shortcuts by entering the name of the application for which the shortcuts is required.
Here is another resource for searching keyboard shortcuts which works on almost the same lines as KeyXL. This resource is known as ‘shortcut world’, which doesn’t offer any search engine like interface to search for keyboard shortcuts, rather it allows you to browse through categories. Categories are designed on the basis of application names, i.e. Chrome, Excel, Firefox, Internet Explorer, Office, Outlook, Photoshop, PowerPoint, Ubuntu Desktop, VLC Media Player, Winamp, Windows, Windows Media Player, etc.
Keyboard Shortcuts for almost all the often used apps can be found here, I hope it gets richer with time in terms of the number of applications for which the keyboard shortcuts are mentioned here.
Try shortcut world, hope you like it.