There are some online sites for feedback on your screenplay, that are good and worth taking about
:
http://www.triggerstreet.co m - Good system, active messageboard with lot's of great advice, regular reviews as long as you review. Limited slightly by 250 word limit, but a good site.
http://www.zoetrope.com - Active messageboard, private office function and internal message system, whilst your script is "active" you will receive quite a few reviews.
http://www.cinefuse.com - Probably the least well known site, but you can get good feedback from here.
Give those above a try, you'll find something you like!