If you used OptimizePress you will love their recently added Overlay feature.
The Overlay module compliments to two-step mini commitment opt-in process. This is already proving to convert better than the average optin form on blog post and even landing pages.
People had previously asked if they can add the Overlay to thier blog post and I saw a recent comment over on OptmizePress blog where someone asked if we can add the overlay feature to the OptimizePress Theme blog.
In this video I show you how I made basic OptimizePress page with Overlay then copied the source code into this blog post with the button to activate the overlay.
I'm sure OptimizePress will add this feature but here is a way you can hack the code and get it working.