When you make a post on your wall you can select the Friends Except option and work your way down the list pressing the Minus button at the side of your friends list. Never tried it myself but just looking at it.
When you post a message there is a drop down menu below that lists who can see your post. You can select your audience here. Alternatively, you may place people you do not want to see your posts on a list and restrict the entire list. In order to create the list you must visit your privacy settings.