re: kids clothes
I find the trick with kids clothes is once you find someone on craigslist to buy, try to get them to be a "regular." Email people just before you post new items. A woman bought a ton from me last spring when she was expecting, and she just came back a few weeks ago. I had everything out on my dining room table and she ended up spending a small fortune! I probably make the same as if I was selling on ebay, but w/o the fees and possibility of someone wanting to return an item.
What is left over goes to a kids resale shop that pays cash up front. Yes, I make less than ebay, but it is a 1 hour appt and I walk out with cash (and my bank has a branch next door! LOL) No posting, taking pictures, mailing, nagging for payments, paying fees, worrying you get a person who puts in a paypal claim... I did the ebay thing and this is so much less stressful!
For play clothes and pajamas, I find making a bag and listing on craigslist works (i.e. bag of 50 pieces of 3T summer clothes for $25)