Actually, Centos is a (free) straight clone of RedHat, minus the proprietary logos and the paid support.
You can try a few of the distros from the top 10 or 20 at http://distrowatch.com/. Many have a LiveCD version ie you just boot off the CD and try it without(!) touching your HDD. Obviously it'll be a bit slower from the cd, but its a good way to see what it looks like.

I like MEPIS. I have tried the CD version and their manual and web looks good to me. I think I will get another HD - D: and install MEPIS as its operating system. This will permit me to isolate Windows from Linux. I have a lot of data, images etc. on book drives G,H,I. to protect. Any ideas on QUICKEN? I use it for my financial stuff.