Almost anything can be done from the command line. But you can't run GUI apps directly. Some apps are engines that just have a GUI frontend that's dispensable. (cdrecord and its various front ends like xcdroast and k3b and so on.) Some are exclusively GUI apps and you need a different console app for the functionality. (mozilla's only a GUI app - but you can surf with lynx or w3m or whatever.) For IM, I've never used it, but maybe
Strictly speaking, running Linux 'from the command line' would be like on my P100 where I don't even have X installed (this time). But you can run almost everything (including GUI apps) from X with just an xterm. Or you can never touch an xterm (in theory, I guess) and run everything from desktop widgets. It just depends on your style and interests and your box's capabilities.