http://forum.xda-developers.com/showthread.php?t=1856574

APN settings for Straight Talk AT&T:

Name: StraightTalk ATT
APN: att.mvno
Proxy: Not set
Port: Not set
Username: Not set
Password: Not set
Server: Not set
MMSC: http://mmsc.cingular.com
MMSC proxy: 66.209.11.33
MMS port: 80
MCC: 310
MNC: 410
Authentication Type: Not set
APN type: default,supl,mms
APN protocol: IPv4
APN enable/disable: APN enabled (tick mark checked but grayed out anyways)
Bearer: Unspecified