This script from Gabe has significantly improved my daily workflow.
I just plop a file into a Dropbox folder (doesn’t have to be Dropbox, really) and the script will upload that file to my S3 Bucket and then copy the URL path onto my Mac’s clipboard. It took me a bit of fiddling to get everything working just right with my different S3 buckets and folder structures within those buckets, but once set up it’s fast and works like a charm.