Some time ago, I went over how to add media files to iTunes automatically. What I didn't mention, though, is that iPhoto has pretty much the same special folder. I'm such a stinker.
Anyhow, if you accumulate lots of pictures, this can be a handy feature. Just put everything you want to keep into that folder, and you can import everything at once when you've got a spare moment instead of having to bring the images in one by one or in a few batches. Awesomesauce! The only difficult part is getting to the darned folder in the first place. To do so, start by finding your iPhoto Library. By default, it lives in [Your Home Folder]> Pictures.
(If you see something in there labeled "iPhoto Library.photolibrary" as well, ignore it. That's not what we're looking for.)
Now, right- or Control-click on your iPhoto Library to bring up a contextual menu, and pick Show Package Contents from it.
You should see a bunch of folders afterward, but the one we're looking for is called Auto Import.
Now you can either drag that to the right side of your Dock for dropping stuff into it easily or put it into Finder's sidebar, for example.
You can also hold down the Command and Option keys together as you drag it to the Desktop (or wherever you want). This will create an alias, which behaves just like the original item when you put stuff into it. Neat!
Make sure not to move the original folder from within the iPhoto Library, or it may not work properly anymore.
After that, anything you drop into that alias or shortcut will get added to iPhoto automatically the next time the app is open. Note that the program keeps that folder clean for you, too—after items have been imported, they're put into their proper location within your Library database and removed from your fancy folder. That's so cool!