Imperial IPA is a stronger version of IPA. It is basically taking the balance of an IPA and applying it to a beer that is 20% stronger. More malt creates more alcohol which needs more hops to balance it out.
Oaked IPA is simply an IPA that has been aged in oak or had oak soaked in it. A good way to do this is with an oak tea, which is what Stone does for their oaked ales.
There are lots of threads on each of these.