Note: this post is from 2007, outbound links may be broken.
Gmail doubles attachment size limit to 20 MB
Gmail upgraded the maximum attachment size from 10 MB to 20 MB (total size of the message).
Gmail Help Center – Maximum attachment size 20 MB
As files tend to get bigger and bigger it seems like a good thing to up the limit, but unless other mail providers will accept these big email attachments you might be limited to sending them to other Gmail or premium mail accounts.
Link via Google Operating System