You can now insert Google Drive files into Gmail. The file can be up to 10GB -- 400 times larger than what you can send as a traditional attachment. Also, because you're sending a file stored in the cloud, all your recipients will have access to the same, most-up-to-date version.
This feature is only available with Gmail's new compose experience, so you'll need to opt-in if you haven't already.
Source: Gmail blog