News about upcoming 3DS and *gasp* Wii software will the focus of the show. No Wii U.
Nintendo will be hosting a Nintendo Direct Event in Japan tomorrow, August 29, at 8 p.m. (7 a.m. ET, 4 a.m. PT). The event will focus on upcoming Wii and Nintendo 3DS titles. Be sure to check out the official Nintendo Direct website for more information about the conference which will be also be streamed live on Nico Nico Video and Ustream. There will be no information about the Wii U at the event.
The information about the conference also came to Japanese gamers on their 3DS via Swapnote in a special message from Satoru Iwata with new stationery (see gallery below).
As of right this time, no other region has announced a companion Nintendo Direct of their own. To find out what time this event is happening in where you live by going here.