Just to add to the earlier post: as a wanna-be uni rider I have
located two brands of unicycles in my local bike shops. The Torker
and the Norco uni’s both are available in 20 inch and 24 inch wheel
sizes.
I read the unicycling FAQ just now but there wasn’t any mention of the
Torker. Which might be preferrable for a first uni?
thanks,
Erin
May i suggest you go to unicycle.com, they have many unicycle to choose from, and are very helpfule. if that is not an option for some resone go with the torker all the way.
joeyErin-
I have a 20" Torker that I bought to learn skills on because it was cheap and has a flat crown. The Torker seat is too small to be of any use but you can upgrade to a Viscount for only $20. The Viscount is not the best but it is fine to learn on, long and wide enough to accommodate adult riders and not as uncomfortable as some would tell you. It will get torn up pretty badly as you learn. I have no regrets about buying the Torker. I weigh 180 lbs and I hop up and down curbs on it all the time. The 20" wheel is inherently pretty strong. A 20" wheel is also quick and responsive. A 24" wheel gives a smoother ride and is somewhat faster. Many consider the 24" as the best compromise for wheel size.
I’m sorry but I have no experience with the Norco. Maybe someone else can give you a quick rundown.
Erin,
Put a lot of worth into what Harper says, he’s good. Just to clarify
that the viscount seat is available from unicycle.com. It really would be a good move for you to call there. You have to pay for
shipping, but you get it back through great advice.
… we know.
Work the maze.
Re: Torker, Norco…
my cousen bought a 20" torker as his first uni. i bought a 24"
cyclepro. I had demolished my cyclepro, and was half way though my
20" savage when his torker gave in. if you are planing on doing
anything besides basic freestyle (i.e. trials, muni, street) or if you
have any expierience in skating, bmxing any of that adn are inclined
to do aggressive tricks, your starter uni will last you about 3 months
max any way you go, so its not a big gamble. get what is easyest, and
it will help you decide what you want to put your real money into. i
personaly would learn on a 20". there stable, best for freestyle,
best for unitrials. freemounting will be much much easyer as most
riders can just step right up onto it as opposed to having to heave
oneself up onto 24".
watch out for number of spokes! I got stuck with a 28 spoke weel both
times, and they will break! if you ride off a curb to many times you
will break it! plus when you break it, you cant simply have your
bikeshop build you a new weel around your hub, cause there would be no
point in puting on another 28 spoke weel. make sure your weel has at
least 36 spokes.
Norco, uni/changeable to MUni
Ok, here it is, i had a norco, well actually 2, a 20" and a 24". Ill start with the 20 " one first. The frame will hold together for awhile, if you land properly on soft ground, i weigh, i think 145 to 50 lbs, and i went off a i think 8 food drop on it, onto soft ground, held together. I think they come with 28 or 32 spokes (not totaly sure, mines 32 i think) im not sure how wide a tire you can fit on the 20" frame, i have a bmx tioga 2.1" tire, if i remember it has some room to go bigger. I eventually broke my 20" frame. (actually my friend broke it, well actualy both of them! 
) they will brake were the bolts hold the frame to hte lolpop bearing holder, (the frame doesnt sit on the bearing holders, just bearly misses, on the 5 frames ive seen) I personally think that the seats, eather a Viscount, or another one that ive seen once, are very uncomfertable, i find that my ass slides down off the back of the seat. And the viscount front is to skinny. But some dont agree with this, and seem to ride them just find, i guess its just personaly preferance.
Now the 24" these ive seen 4 of, thats the one that ive been riding since last summer, till alittle while ago, you can fit up to a 2.6 " tire. i rode a kenda kolassal dh tire, it just fit, not sure if you couldd squeeze a 2.7 in but definatly not a 3". Again the problem was the seat, which i switched, and the frame were it cracks, at the base. As youve probably seen that the norco frame is not a flat crown, so you cant put your foot on it. You CAN put brakes on the norco, i my self have done it by taking a old bike forks, and cutting them in two places above and below the brake boses, about 1.5" above and belowe if you can. Then cutting that down teh back so you can bend it to the shape fo the fram, then attaching pipe clamps, around it and the frame to hold it in place, a cheap and easy way to attach breaks, the leaver part, i useed a diferent seat so my way of doin it would be differnt, you can see a picture of a brake mount on the gallery on this site, its one of a Coker, witha a blue Viscount seat. Another person ive talked to on icq also has attached brakes, im not totaly sure how he went around doin this, but i gues by welding them on.
The rim, i myself have a 28 spoke hub and rim on it, its not a stong rim, as its ment to be a road unicycle, my friends got 32 spoke hubs and rims, on thers, so i guess it changes wiht the unicycle what you get. I have just recently started to warp my rim, after breaking a spoke on it, after going off a small drop, ive been doing small drops on my unicycle for about 9 months i think. All about 3.5’ onto concreat. Depends on how you land, and how heavy you are though, my friends have warped their rims pretty bad. The crank arms, they to me have held up, im still using the same hub, axle, rim, ive just switched teh frame. My crank arms havnt warped or broken, although im sure they can. The hub, no idea about how good it is, proably best bet is that its not very strong. The norcos ive seen cost about 130 to 145$ i think, i forget. But thats al i got to say. About the Torker, im not sure how good that is, never rode it, but im sure that its a good uni. well hopefully i helped alittle. later. 
I’m just a beginning rider and have a 20" and 24" Torker. They seem to be pretty good for an inexpensive uni (I paid $83 including shipping), although I can only compare them to the POS I bought first (then got rid of). They have 36 spokes, and I think they have a better seat than they used to. The seat hasn’t bothered me, but I don’t get to spend too much time on it yet :).
Art