Well, it depends on who you are looking to sell to and how you want to conduct business. Theoretically speaking, endusers are the best way to go but not everyone is cut out for following the enduser path. It takes a lot of time and requires much patience.
Personally speaking, I've met a lot of "success" in forums such as Namepros. You're going to encounter more of the reseller market here, but domains sell quicker and if you're looking just to make a few bucks, then this is the place for you. Forums place you in quick communication with people although they aren't endusers. This means you probably won't get the big $'s but you can still do well.