Just compare the ScalaDoc of different Scala versions.

Things which come to mind (comparing roughly 2.8 (released 2010-07) to 2.11 (released 2013-03)):

Classes (just from the top-level scala.* package):

  - Application
  - Cell
  - cloneable
  - CountedIterator
  - NotDefinedError
  - NotNull
  - Responder
  - serializable

Complete packages:

  - scala.actors and subpackages
  - scala.collection.interfaces
  - scala.concurrent (still exists, but its contents have been replaced completely)
  - scala.dbc and subpackages
  - scala.mobile
  - scala.reflect.generic
  - scala.swing and subpackages
  - scala.testing
  - scala.text
  - scala.util.automata
  - scala.util.continuations
  - scala.util.grammar
  - scala.util.logging
  - scala.util.parsing and subpackages (includes parser combinators and JSON)
  - scala.util.regexp
  - scala.xml

(This of course doesn't include things which were demoted from scala to other namespaces like scala.util, scala.runtime, scala.annotations ...)

The list is certainly incomplete anyway...