Google Alerts does not have an official API, but sometimes you just need to create a lot of alerts. I did, so I pulled some code together from Stackoverflow and built my own PHP class for creating Google Alerts in bulk.
One caveat is that I didn't build any way to remove alerts in bulk ( although you could definitely use this base class ), so be careful when creating alerts in your primary account. It's easy to flood it with alerts, and then not be able to delete them. I actually created some new accounts to create bulk alerts in.
Also, this class currently logs in for every alert it makes, so it's not super fast. Some cleanup could definitely be done.