Also, try www.photo.net, I've had some good critique from the users there. Only problem is (I think) the photos are compressed, I'm not sure though.
As for these pictures, I'm not a proffesional on portrait pics, but I'd say that a)If you are going to use natural light, try and make sure that you don't get this light/dark side affect. If you are close enough, you can use a fill flash, but remember that using focal lengths of above 80mm and your flash isn't going to be as useful, and if it can reach the tones will be quite harsh.
B & W is an opinion, I guess. If you want a moody picture, that has alot more feel to it, then you should use B & W slide film. However, you have good use of DOF here, and some nice (if sometimes 'forced') poses. Very good for a couple of first attempts!! I look forward to seeing more.
If you find Jason Milligan, I am pretty sure he can help you as he has had experience in this type of photography (he has stunning models too!!!). I forget what username he uses though