Is it possible to, say, email files via attachment to your Dropbox account? As opposed to manually placing the file on the Dropbox folder on your computer?
If you're open to using a third-party service, you can use If This Then That. There are a number of ways to do that, either by sending email to IFTTT's mailbox (
firstname.lastname@example.org) or to your own as a trigger, and then uploading the file to your Dropbox.
I used the email channel to set a trigger where if I send an email message from my registered address to IFTTT's mailbox with
#dropbox in the subject, that'll use the Dropbox "add file from URL" action to save a file to the
IFTTT/email directory in my Dropbox and the rest of the subject as the filename.
(Here's a public recipe that essentially does the same thing.)