I was going to write a tutorial on how to email multiple iPhone photos at one time, but really, all you have to do is follow the steps in my "How to delete multiple iPhone photos" tutorial, and instead of tapping the "Delete" button, tap the "Share" button. After that, choose "Email", and you'll be taken to the iPhone email app.
An important thing to know is that you can only share/email a limited number of iPhone photos at one time. On my iPhone 3G, using the iPhone OS version 3.1.3, I can only send five photos in an email at one time.
I should also note that when you tap the "Share" button, you can send multiple photos by email or MMS. I'm not a big MMS user, but that option is there.
Okay, enough said. Again, just follow the instructions in my "How to delete multiple iPhone photos" article, and just tap "Share" instead of "Delete", and then tap "Email", and you'll be able to email multiple photos from your iPhone.