From the WHL, some guys to watch for 07 are Hickey, Hamill, Sutter, Gillies, Alzner, Repik, Hamill, Plante, Sonne, Ellerby, Blum, Negrin, Mucha, Bowman, King...
I'm not entirely comfortable ranking all of them, particularly guys like King, Bowman, Gillies and Sutter who I really only get a chance to see a couple of times a year if I'm lucky, but I can say a few things about some of them.
Hickey is definitely my favourite as of now. He really must have scouts salivating with his combination of size, great mobility, incredible poise for a 16 yo, and general all around high quality play that is remarkable for a 16 yo defenseman playing in the WHL (Luke Schenn also falls into that category, but hes a late 89 and not eligible until 08). Shows pretty good offensive potential, and he is already strong and solid defensively. It's hard to predict these things a year in advance, but I am going to (stupidly) try anyway and say he goes first among WHL defensemen.
edit: apparently he is only 5'11, I thought he was 6'3. Well, that takes a little of the luster off. Not sure where I got 6'3 from.
Hamill has great talent and has produced well in defensive Everett, but also remember he is a late 88. Since he came into the league at 15 in the playoffs I've liked Hamill quite a lot, despite his intensely annoying habit of constantly chewing on his mouthguard while he plays. I hear a lot of talk about him being a great skater, and while he is pretty quick, I think he has a lot of leg strength to add, and probably could benefit from a quicker first step. He isn't the biggest guy, so I would like to see him become an elite skater to solidify his first round status. Great puck skills though, and very clever in the offensive zone. Likes to set up down low on the left side and thread passes and one time shots (he is right handed). Effective defensively, too.
Repik is an interesting one. He has some some outstanding attributes that I think are going to carry him to a first round selection. He has good speed and good acceleration, but more importantly he is very shifty and uses hard cuts and change of direction and change of pace extremely effectively. That's something that can really translate well to the NHL. Also has an instinctive ability to be in the right place and a good nose for the net. Good finish with good hands and patience in tight. Not afraid to mix it up at all, either. He had an amazing start to the season this year, but tailed off in the second half, likely largely due to fatigue. I fully expect him to have a huge year this season and find himself selected in mid first round.
Blum is another guy I see a lot of in Vancouver. Like Hickey, he has poise and intelligence beyond his age. Great offensive touch, loves to sneak in from the point, and really matured into a solid offensive defenseman last season and benefitted from playing with Mark Fistric. Not a big guy, nor is he intimidating or overly physical, but he is a mobile and agile skater that can keep guys outside. Definitely does need to get a lot stronger to win some more of those tough battles. If he can convince scouts that his skating, offensive ability, and intelligence are elite, and be smart in his own zone, I think he can overcome his size and be picked in the first round. If he has trouble handling bigger forwards, or doesn't have a big offensive year, he could find himself slipping. Should benefit from the recent drafting mentality of scouts and GMs regarding the new NHL.
I bit off more than I could chew with all these prospects I was planning on writing a little about. Maybe I'll try to write more a little later.
Overall, though, my early list from the WHL Western Conference for 07 as of now would probably look like this:
Hickey
Hamill
Repik
Ellerby
Mucha
Blum
Negrin
Sexsmith
Bowman
It is important to point out, however, that it gets pretty blurred for me after the top few, and I fully expect this to be subject to drastic, drastic change over the course of the next season. Early rankings are fun, but beyond a couple of really strong feelings (like Hickey), it's very tough to predict this early.