There are literally hundreds of Linux distributions. At LinuxHow2, we focus on the most popular distros; however, we don't want to exclude the thousands of individuals that prefer one of the less commonly used distributions.

We at LinuxHow2 are really interested in what other people are using. Please sign up to our forum and post your OS. Check out the thread here What do you use? 

Some of the more popular distros that we didn't mention so far include Damn Small Linux and Puppy Linux; both of these distros are extremely lightweight and great for an aging PC, I installed Damn Small Linux on a 6 year old Celeron-based PC (that somehow once ran Windows XP). The PC was taking 25 minutes to boot; it was taking ten-fifteen minutes to load each application; it was essentially useless in the real world. After installing Damn Small Linux to the hard drive, it boots in under 30 seconds; it loads apps instantaneously; it uses hardly any memory, and I don't hear that crunching, grinding noise from the hard drive anymore (you know the kind of noise that reminds you of your stomach growling after you ate that cheese and nacho dish at the bowling alley). 

There's also the new gOS operating system that comes bundled with the Everex line of computers. This OS has got to be gaining in popularity after all of the recent sales of the the Everex PCs in Wal-Mart stores. I haven't personally tried it out yet; if you have, let us know what it's like in our forum What do you use?. From what we've read, the system is extremely Google-friendly; it defaults to using Google's e-mail software (gmail), Google's spreadsheet and docs, Google's instant messenger, and more. Google's conquered much of the search world, and with the help of this blossoming PC, it might help conquer the desktop software world too.