Videos taken from your iphone or ipad are imported into iPhoto when you sync your device to iTunes, but it's not very clear how to get those videos out of iPhoto. You can't use the Share -- Email option, because iPhoto only lets you share photos via email.
To share videos over email, export the video as if it were a photo, and iPhoto will convert it to a Quicktime movie format that you can attach to an email or upload to YouTube.
First, sync your iphone or ipad with iTunes, so that your photos and videos are in iPhoto. Open iPhoto and find the video you want to export.
Click the File -- Export menu option and then press the Export button.