What were your difficulties with other storage?
S3 is as easy as:
s3cmd put FILE [FILE...] s3://BUCKET[/PREFIX]
Dropbox is automatic, just move a file to a local directory. They have CLI tools, though. If you want the public url, it's just:
$ ~/bin/dropbox.py puburl ~/Dropbox/Public/file.zip
If you don't want dropbox running all of the time, just use the 'start' and 'stop' arguments to dropbox.py.
References: http://s3tools.org/usage
http://www.dropboxwiki.com/tips-and-tricks/using-the-officia...