www.linuxiso.org all your linux distribution needs
IT also has forums for all the major ditributions. So you can look thru it for help and or thoughts about why to use this or that. People there tend to be knowlegeable about a variety of varients. If you decide on one permentently then it'll give you a link to the distro's forum and page
Knoppix tends to be the popular one to use to see what linux is like without plunging all the way in and installing it on a hard drive
glad you want to join in the linux fun. *counts 28 hour and going for compiling kde on the latest*