Just Wii Sports Resort.
Motion Plus comes with Grand Slam Tennis. It's not worth getting just yet though. I didn't find the difference in sensitivity to be that amazing.
( WHARRGARBL, Wed 24 Jun 2009, 16:56, archived)

Is wii motion plus
a new controller?
( CowJam, Wed 24 Jun 2009, 17:02, archived)

it's an add on
supposed to give 1:1 motion detecting
( manolith hooray for me, Wed 24 Jun 2009, 17:08, archived)