i am a bit of a cast on fanatic.
back in march i did a 4 part series about cast on's (followed by a single page about cast off methods.)
you can see it here
there are differences between cast on's, and i recommend/suggest taking a partial ball of yarn, or an odd lot ball, and making a cast on sampler. (i show mine one of the pages)
then you can
1--learn a cast on
2--see how it looks
3-see how stretchy (or firm) it is
4--see how well it matches a standard (or other!) cast off.
I list 35 cast on's, and there are more!
Part 4 of the tutorial is a page of links to On-line video and photo tutorials, list of reference books, and other sources of info on how to work each cast on.
of all the cast on's i know, i must say i use LONG TAIL (aka thumb and sling shot) OR A VARIENT (norwegian long tail, braided long tail, 2 color long tail, etc) about 50% of the time.
my next favorite is a tubular cast on (there are at least 3 ways to do this cast on!)
and for knitting in the round, i like both the emily ocker and Loop cast on.
some cast on's are prettier (my current blog entry has a pair of socks with a channel island cast on.. very pretty, very stretchy (not to hard to do, but there aren't any good on line instructions either, so its hard to learn!)
and some cast on's are more useful (LONG TAIL!) but you, too could spend a life time learning cast ons!