With two children and a part-time job, I've found on line writing groups to have a convenience factor that works for me. My writing friends and I made our own. We've done it on LiveJournal by creating our own closed community (that way when you post your work, it's not public). One I'm currently in (though I'm on hiatus while I beta a friend's novel) works like this:
5 members
All members post each Monday, reporting their writing progress on the last week and goals for the next week. (Great for keeping us accountable) We really focus on the writing, so this doesn't become a social hour. This is required - members must be timely and offer support/comments to the others, or the cohesiveness and rapport suffers.
One member per week posts a piece for critique and all other members are required to post critiques in a timely fashion, by adding comments to the post. (If you're familiar with LJ, you'll know what I mean here.)
IF a member doesn't have a piece to post for critique, then he or she is welcome to bring up any writing related discussion or ask a writing related question.
I think this group has worked out well, though we've found it REALLY makes a difference if all of the members are on the same page as far as seriousness about the craft, and commitment to participating in the group. If a member is lazy about posting or commenting on others' posts, it really brings the morale down. We've had a bit of turnover due to these issues, but the core of the group has remained consistent.
c.e.