PatternReview website, I found it really cumbersome to use and can never find the actual patterns that must be represented on there. It also doesn't feel like a community as much as MSC does.
I can recommend it!
Pattern Review can only be used properly after you log in but unfortunately it isn't clear where you do that until you try to find something and a red stripe across the screen asks you to log in. It is really difficult to see. I just had another look: there is a Log In link that you need a magnifying glass for.
Fairly new is The Fold Line:
I am enjoying looking at all the different kinds of features. Just like on MySewingCircle you can befriend others. This site seems to attract more independent designers publishing their patterns.
I like their Forum the best.
I have also occasionally logged onto the SewingForum.com - link here. This is the old bulletin board style.
What sites do you use?