well for exmaple linux mint uses Cinnamon desktop (based on Gnome3) they developed. they also fixes some bugs from Ubutnu "solutions". but as i was trying them they always used too much RAM and forced disk into swapping prematurely.
you can try Debian (Ubuntu's father) that is slightly different and for some reaosn it uses less ram and seem to be lighter on resources. A good version of it is Chrunchbang (i mean easy for new peopel to install)
then you have the various rpm based distribution and each is a bit different. you have the Fedora (Red hat testing ground) that has plenty of latest stuff, OpenSUSE (used to have best KDE integration), Arch linux - build your own distro kind of thing (can be very light on resources if oyu know what you're doing), super stable very long temr support RHEL based linuxes (CentOS, Scientific Linux).
then you have the super small ones - Slitaz, DSL, Puppy, Tiny Core - some of them might even work on now ancient 486cpu...
then there are specialist ones -
for example GUI server/NAS: Zentyal, Openmedia vault
or rescue, backup: rescue disk, gparted, redo backup
or "hide the user from regime": Liberte linux, Tails
then you have soem with different idea of OS behind it such as Turnkey Linux
so many of them out there. and plenty are interesitng just to try them.