Check out this article from the New York Times online. Compact fluorescent bulbs are everywhere right now and offered in a lot of replacement shapes so consumers can easily change out their bulbs without replacing fixtures. It looks like it is LED's turn. The article talks about the unique heat dissipation required with some of these LED replacement systems and the even more unique designs they are taking. The prices are still high but as more manufacturers get involved prices should drop.
Here is an example of one manufacturer, Lighting Science.