As for Mickey and Minnies houses... it has to do with the closure of Toon Town. The plan I believe (some one can correct me if I am wrong) is to turn that area into Pixie Hollow/Princess area.
So here is a list of current and upcoming closures/refurbs... I put some of the one more important ones. (at least more important in my eyes) in red.
Refurbishment/closure information is subject to change without notice and should be confirmed just prior to visiting. Updated information is available at
http://www.disneyworld.com
Current
* Osprey Ridge Golf Course closed through 6/17/10 for refurbishment.
* Sand Trap Bar & Grill closed through 6/17/10 for refurbishment.
* Oak Trail Golf Course closed through 6/20/10 for refurbishment.
* Magic Eye Theater at Imagination! (Epcot) closed through 7/1/10 for reburbishment.
* Cantina de San Angel (Epcot) closed through Fall 2010.
Upcoming
* Lake Buena Vista Golf Course closed Mondays only 6/21/10-7/26/10 for refurbishment.
* Palm Golf Course closed Tuesdays only 6/22/10-7/27/10 for refurbishment.
* Magnolia Golf Course closed Wednesdays only 6/23/10-7/28/10 for refurbishment.
* Osprey Ridge Golf Course closed Thursdays only 6/24/10-7/29/10 for refurbishment.
*
"it's a small world" (Magic Kingdom) closed 8/1/10-10/22/10 for refurbishment.
* Palm Golf Course closed 8/2/10-8/8/10 for refurbishment.
* Magnolia Golf Course closed 8/9/10-8/15/10 for refurbishment.
* Lake Buena Vista Golf Course closed 8/16/10-8/22/10 for refurbishment.
*
Toy Story Midway Mania! (Hollywood Studios) closed 8/16/10-8/28/10 for refurbishment.
*
Walt Disney: One Man's Dream (Hollywood Studios) closed 8/16/10-11/2/10 for refurbishment.
* Osprey Ridge Golf Course closed 8/23/10-8/29/10 for refurbishment.
* Oak Trail Golf Course closed 8/30/10-9/3/10 for refurbishment.
*
Star Tours (Hollywood Studios) closed 9/8/10-2011 for refurbishment.
* Typhoon Lagoon closed 11/1/10-12/31/10 for refurbishment.