I have recently joined Scribophile, an interesting peer-review site for writers looking to improve through constructive criticism. They offer a pretty expensive ($9pcm) premium membership, but of course I’ve only got the free membership because I’m not far from impoverished student-hood!
The site runs on karma points, so you have to critique in order to obtain points, which you in turn ‘cash in’ to post your own writing for comment. Authors as well as other readers/critics can then ‘like’ your critique (gaining you extra karma points!), as well as ranking your critiques as thorough, enlightening, encouraging, or constructive.
The site is great fun, although I think it will take me a little while of concerted effort in order to get into it. There are a lot of multi-chapter works being posted, so it can be a struggle to tackle critiquing a chapter when you haven’t read the seventeen before! I have started with things that are early in their development (i.e. chapters 2/3) or short stand-alone fiction pieces and hopefully I will be able to start following some longer pieces of work as they are developed through re-writes and subsequent chapters.
I’d recommend it so far, but the jury’s out until I’ve posted something of my own.