Incomplete List of HTTP Frameworks
The Play framework is built using Akka, and is well suited for building both full web applications as well as REST services.
The Spray toolkit is built using Akka, and is a minimalistic HTTP/REST layer.
If you are using Akka Mist (Akka's old HTTP/REST module) with Akka 1.x and wish to upgrade to 2.x there is now a port of Akka Mist to Akka 2.x. You can find it here.
There are a bunch of other alternatives for using Akka with HTTP/REST. You can find some of them among the Community Projects.