What iPhone apps are available for sending bulk SMSs? What iPhone apps can I use for sending bulk SMSs?

Hopefully something very simple to get started with....
Built-in Group Messaging

On any iPhone with iOS 4 you can enable group messaging which will allow you to message a group and for responses to be sent to the whole group:


Open Settings
Tap Messages.
Finally, flip the Group Messaging slider to On.


Other soltions include:


Mass Text Message
Beluga
textPlus