Let's start with the obvious. You'll need a computer (or access to one) that you can use to complete coursework online. While programs typically don't require you to have a brand new machine, some older computers may lack the processor speed and memory space you'll need. Schools offering online classes often the provide minimum technical requirements at their websites. You can also contact an instructor or technical support for information.
Of course, you'll also need access to a high-speed Internet connection to take online classes. Again, technical specifications for connections and modems can vary between schools. For example, you may need broadband to participate in some programs while dial-up may be okay for others. As with computer hardware, it's a good idea to check with the institution offering classes.
When you have adequate hardware and Internet connectivity, you can turn your attention to software. Many online programs require you to have common Microsoft programs such as Word, Excel, PowerPoint and Access. Depending upon your academic discipline, you may also have to purchase specialty programs to complete your studies.
Taking online courses, you may also be expected to download popular applications that allow you to connect and collaborate with others. Adobe Reader, commonly used in online learning environments, allows you to view PDFs and share documents with others. You may also be asked to utilize a media player (like Windows Media Player) or communications tools (such as Skype or Google Talk). An instructor can tell you what applications you'll need for a class.
While not all courses will require it, a portable media device - such as a smartphone, mp3 player or Internet tablet - can be very useful when taking classes on the Web. Many online courses feature social networks, discussion boards and other opportunities to communicate and work with classmates. Mobile devices can allow you to field questions and make contributions when you're on the go. Many have cameras that can also help you share images with peers and teachers via classroom blogs, wikis or eportfolios.