More than you'd expect, but probably fewer than you would like. The most popular business application suite in the world - Microsoft Office 2000 Professional for Windows - is not available, and Microsoft says that it currently has no plans to port Office to Linux. In contrast, Corel has spent more than a year porting its WordPerfect Office suite to Linux, and the finished product is now available. One of the Corel suite's main goals is to achieve interoperability with Microsoft Office.
In some instances where popular apps are unavailable in Linux versions, open-source alternatives are plentiful. So even though Adobe doesn't make a Linux edition of Photoshop, there's an excellent free alternative, The Gimp (www.gimp.org). This package matches many of Photoshop's features and has a few extras. Similarly, your digital camera didn't come with Linux software to view its pictures, but download a free copy of gPhoto from www.gphoto.org, and you're fully equipped to view your images.
There are hundreds of Linux applications, though most are either highly specialised (like 3D object modellers) or targeted at servers (like robust databases). One exception involves Internet applications. In addition to current versions of Netscape Communicator and Navigator for Linux, there are dozens of e-mail apps, news readers, and more.