I've pasted the 20 fastest growing (2010-2012 in absolute terms, not by rate) here and read around a bit. Two in the Northeast (quite a turnaround - Boston and New York, unless you count Washington), none in the Midwest. Boston includes Suffolk, Essex, Norfolk, Middlesex, Plymouth, Rockingham and I think Stafford in NH) Typical sunbelt growth appears to have returned to Phoenix, Orlando, the Inland Empire, Charlotte, Miami and Atlanta. Las Vegas not so much. Texas growing with continuing oil/gas boom. Seattle and SF growing from tech. San Diego and LA growth continues to show post-2000 long term slowdown. First figure 2010, second figure 2012, third figure 2012-2010.
Dallas-Fort Worth-Arlington, TX 6,426,210 6,700,991 274,781
New York-Newark-Jersey City, NY-NJ-PA 19,567,407 19,831,858 264,451
Houston-The Woodlands-Sugar Land, TX 5,920,456 6,177,035 256,579
Washington-Arlington-Alexandria, DC-VA-MD-WV 5,636,232 5,860,342 224,110
Los Angeles-Long Beach-Anaheim, CA 12,828,842 13,052,921 224,079
Miami-Fort Lauderdale-West Palm Beach, FL 5,564,657 5,762,717 198,060
Atlanta-Sandy Springs-Roswell, GA 5,286,732 5,457,831 171,099
Phoenix-Mesa-Scottsdale, AZ 4,192,887 4,329,534 136,647
Riverside-San Bernardino-Ontario, CA 4,224,851 4,350,096 125,245
San Francisco-Oakland-Hayward, CA 4,335,391 4,455,560 120,169
Austin-Round Rock, TX 1,716,286 1,834,303 118,017
Seattle-Tacoma-Bellevue, WA 3,439,809 3,552,157 112,348
Denver-Aurora-Lakewood, CO 2,543,478 2,645,209 101,731
San Antonio-New Braunfels, TX 2,142,508 2,234,003 91,495
Orlando-Kissimmee-Sanford, FL 2,134,411 2,223,674 89,263
Boston-Cambridge-Newton, MA-NH 4,552,402 4,640,802 88,400
San Diego-Carlsbad, CA 3,095,308 3,177,063 81,755
Charlotte-Concord-Gastonia, NC-SC 2,217,035 2,296,569 79,534
Minneapolis-St. Paul-Bloomington, MN-WI 3,348,859 3,422,264 73,405
Portland-Vancouver-Hillsboro, OR-WA 2,226,009 2,289,800 63,791
Dallas-Fort Worth-Arlington, TX 6,426,210 6,700,991 274,781
New York-Newark-Jersey City, NY-NJ-PA 19,567,407 19,831,858 264,451
Houston-The Woodlands-Sugar Land, TX 5,920,456 6,177,035 256,579
Washington-Arlington-Alexandria, DC-VA-MD-WV 5,636,232 5,860,342 224,110
Los Angeles-Long Beach-Anaheim, CA 12,828,842 13,052,921 224,079
Miami-Fort Lauderdale-West Palm Beach, FL 5,564,657 5,762,717 198,060
Atlanta-Sandy Springs-Roswell, GA 5,286,732 5,457,831 171,099
Phoenix-Mesa-Scottsdale, AZ 4,192,887 4,329,534 136,647
Riverside-San Bernardino-Ontario, CA 4,224,851 4,350,096 125,245
San Francisco-Oakland-Hayward, CA 4,335,391 4,455,560 120,169
Austin-Round Rock, TX 1,716,286 1,834,303 118,017
Seattle-Tacoma-Bellevue, WA 3,439,809 3,552,157 112,348
Denver-Aurora-Lakewood, CO 2,543,478 2,645,209 101,731
San Antonio-New Braunfels, TX 2,142,508 2,234,003 91,495
Orlando-Kissimmee-Sanford, FL 2,134,411 2,223,674 89,263
Boston-Cambridge-Newton, MA-NH 4,552,402 4,640,802 88,400
San Diego-Carlsbad, CA 3,095,308 3,177,063 81,755
Charlotte-Concord-Gastonia, NC-SC 2,217,035 2,296,569 79,534
Minneapolis-St. Paul-Bloomington, MN-WI 3,348,859 3,422,264 73,405
Portland-Vancouver-Hillsboro, OR-WA 2,226,009 2,289,800 63,791