Linux is well known to run on all kinds of hardware from the oldest machines to the worlds super computers, and am always coming across friends that have older machines with only half a gig of RAM but most modern desktops recommend at least one gig of RAM. While it might not cost much to upgrade, I still think that a PC can still be comfortably usable without upgrading.
That's where Bodhi Linux comes in, it is a fast and fully functional desktop that runs on LXDE. Have done an article featuring Linux Mint running LXDE on a netbook, and Linux Mint is a really good distro they just don't have being lightweight as their main goal. Bodhi Linux is a Linux Distribution that focuses on the fast, customizable, and beautiful Enlightenment Desktop.
The minimum requirements to run Bodhi Linux are only: 300+MHz CPU, 128MB RAM, and 2.5GB hard drive space!
Not to mention it looks pretty good by default.
Watch a review of Bodhi Linux by one of the best Linux podcasts out there Jupiter Broadcasting
Linux Action Show - Bodilicious Bodhi Review
Bodhi is a semi-rolling release based off of the LTS versions of Ubuntu, so that means you'll get the latest version of GIMP or Blender without having to add PPAs. They have a pretty active community and a really awesome art section, that any geek would love at Bodhi Art Wiki
Download a copy of Bodhi Linux: Bodhi Linux
Bodhi is also availble (in alpha stage) for mobile devices. Am looking forward to trying Bodhi on a Nexus 7 tablet, the interface has been changed to work for touch devices, and looks promising.
Download Bodhi for ARM (mobile) devices: Bodhi ARMHF
Video of Bodhi Linux on a Nexus 7, by the main developer of Bohdi Linux.