A few weeks ago, I open sourced a tool I often use when developing new products. Meet under_construction - a JQuery utility for hiding/overlaying elements of a design that haven't been developed yet.
I wanted something that it is entirely unobtrusive and W3C compliant. No funky markup, and when you build a feature, you just remove the pending class from the elements you want to expose.
I'm planning to add more features. It would be great to add labels to the overlays so the stakeholder will know when that feature will be unveiled like Thoughtbot's Mile Marker. I'm planning to implement that as another class. Of course, the design principal of staying unobtrusive and standards compliant will remain paramount.