There's no app that I'm aware of, but you can enable mobile uploads from your Photobucket settings. After you've confirmed your phone number, it will generate an e-mail address for you to send pictures to. After a bit of processing, the image will be uploaded and available in your account.
once you do this, create a contact for the photobucket email addy. then, just navigate to the picture you want to upload and hit menu>email and pick photobucket.. almost as easy as facebook.
i actually figured that out on accident.. i made a contact so i could remember the addy, and it just mentally fell in place the next time i wanted to upload a photo.
