the most suited distro for starters is mandriva or ubuntu.
mandrivared:it gives a feel of windows working in envirment.
redhat 9:It is a age old distro which is preceed by the fedora core 5.so no point going for it.
knoppix:It a live envirment that is it runs thorugh cd so the performance will be very slow.it is useful for people who just want to feel what linux is all about.u are serious of learning linux u should install it on your harddrive to unleash the true power of linux.
Fedora core 5: i very good distro indeed, many of my fellow members are using this.but its mainly for advanced ppl.
ubuntu 6.06:my personnel choice.its debian based package mgt sys is very good. but the problem is it comes with very less softwares so u have to download them from internet.plus point it has indepth support in form of malling list, user groups, forums,irc's.and lots of official documentions
see my personnel opnion lets see whats others say about it
[edit]learn linux online from start:
do u want to learn linux