How many football teams in division 1-A?

As of 2012 there are a total of 124 (120 full members, 4 transitional) teams.

The newest members:

Massachusetts Minutemen

South Alabama Jaguars

Texas State Bobcats

UTSA Roadrunners

Three new members making the transition:

Georgia State Panthers: 2013

Charlotte 49ers: 2015

Old Dominion Monarchs: 2015