I have had success with Craigslist on the items I consider "bigger ticket items," such as baby equipment and higher-end brand clothes (Gymboree, Hanna Anderson, etc.) I've never tried the "lot of clothes" approach, as someone mentioned, but it seems to be popular.
When using Craigslist, I have seen a much better response to ads in which my photos are REALLY good -- well-lighted, multiple shots, close-ups, etc. These meant more time and effort for me. Then there's answering all the ad inquiries, setting-up dates/times for people to come look at the items, re-contacting respondents when the first responders are no-shows, etc. It's difficult for me to find the time to devote to this effort, so I've decided to stick to Once Upon A Child for selling the playclothes and save Craigslist for the more valuable stuff.
Before pricing my non-clothes items, I make a stop at Once Upon a Child and take note of the prices they are charging for the same items. Since you know you would not be paid the same amount that they have priced the item, I consider getting that same store price through Craigslist a win (and worth the time and effort!) With very few exceptions, I have been able to get as much or more than what people would pay at Once Upon A Child.
One last thought...if you are going to the effort to list items on Craigslist, I would go through the entire house and find other stuff you want to get rid of as well. Since you'll have the camera out and will be writing the ads, take the opportunity to get rid of some of the non-baby stuff around too. Do it all at the same time!
And have fun! It's neat when you've got a bunch of people wanting to come buy your stuff!