Fun or interesting project ideas to utilize two XP-era computers and learn about Linux by doing?

I am new to Linux. I've been using it on and off for the past year, since I got this laptop. I upgraded to Windows 8 when it came out and then set up dual boot with Ubuntu, which I recently upgraded. I also have an old desktop i recently got "working" which I put Ubuntu on, and an old Acer laptop on which I installed Fedora 19. Both of these latter two computers are running hardware from the Windows XP days. I'm looking for some ideas on projects to do with both or either of them, the desktop and the notebook running Fedora. Like I said, I'm new to Linux, but I enjoy learning by doing so I am hoping to get some ideas for ways I could utilize these current dust collectors and learn in the process. The desktop has no monitor so I use it with my HDTV via a VGA cable, and it's video card is probably the newest hardware in it - Ubuntu at least doesn't look too bad on the tv. But, since it requires the TV for a monitor, I was thinking something in media-related for it. Any resources or ideas from people who have done so is welcome. And it isn't a requirement of mine to stick with those distros necessarily. Thanks in advance!