Dropbox would be your best try. But it is still pretty convoluted just to copy photos/videos over.
You just view the picture in Dropbox and then download. The benefit of Dropbox is that any photos placed into your camera roll get uploaded to a folder on Dropbox. Enough uploads and Dropbox will increase your storage to a total of an additional 3GB over time.
Note that any picture you download to your camera roll from Dropbox is seen as new and will be thus copied to the Camera Uploads folder in your Dropbox folder.
If you have a Mac another option would be PhoneView. You get direct access to the local file system and can place photos directly into the Camera roll. You have to delete the database file and restart your phone though so that your iPhone rebuilds the DB and sees your new photos. The advantage here though is you can add as many photos at a time as you wish.
There's also Eltima Syncmate. But I have not used it for the iPhone, only my old Windows Mobile phone so IDK if it supports photos or not.