People ask this a lot. Sounds like someone needs to step up.
It's not going to be me, since I've already got two different groups on the go. But I can tell you guys what my group does, since it works well for us:
-7 members (8 is probably max if you're actually meeting)
-range of skill levels, all the way up to one member who's IMO publishable with her latest novel
-meet every two weeks via Google Hangout
-read one novel at a time, in chunks of 20-30k words, generally resulting in four meetings per novel over two months
-give feedback one person at a time, limited to five minutes, with everyone else muted and no responses from the writer (we later added a second round since people sometimes had stuff they really wanted to say that they hadn't gotten to in their allotted five minutes). We mostly stick to major stuff, with minor things being commented into the text while reading and sent over after the meeting.
-people can commentate or say "ditto" in the chat window
-feedback generally takes the form of pointing out: things I didn't believe, things I didn't care about, things I didn't understand, and things I thought were cool (we started out this way, but since we've gotten to know each other better we've moved on to more nuanced critiques that are more diagnostic. "I felt this way and I think this is why." We still try to stay away from prescriptive crits: "This didn't work and here's how you fix it."). This is done politely and kindly. We don't want to avoid pointing out problems, but we want to do it in a way that isn't hurtful.
-after everyone's done with their crits, the writer can ask for clarifications or ask questions about what worked and what didn't (they should under no circumstances be arguing with the critiques). Common questions in our group include: "What do you think will happen next in the story?" "What promises do you feel have been made to you as a reader that you expect to have fulfilled later?" "What do you hope will happen, and what do you fear will happen?" etc. Questions can be asked to individuals or in general. If in general, we usually respond in the same order we gave critiques.
The tricky part about actually meeting, even over Google Hangout, is finding a time that works for everyone. It makes a huge difference, though: not only can you express strong critiques nicely, when they might just come off as hurtful through text-only, but you really get to know the other folks in a way that doesn't happen as strongly through text. I think this is a big part of why we were able to move more to diagnostic crits from the basic stuff.
Some groups do multiple things at once. My second group focuses on short stories, and does three at a time, usually. This could work for novels, doing them a few chapters at a time, but it'd mean you're stretching them out over a really long period of time, in a way that makes the story more confusing and ruins any sense of what the pacing is. One at a time works pretty well for us, and so far no one has ever felt that they're not getting their fair shot at critiques.
Anyway. If I were to try to put something together here, I'd gauge interest, find out availabilities, and then put together something similar to the above, adjusting as needed to fit the needs of the different group.