Rapidly rotate an image
In the Windows OS, you can right-click on an image and choose a Rotate command. The Mac OS lacks such a feature, but you can produce something darned close with Automator.
Launch Automator (in your /Applications folder) and in the template chooser that appears choose Service. Click Choose. In the resulting workflow window, configure the pop-up menus at the top of the window to read Service receives no input in any application.
Select the Files & Folders library and drag the Get Selected Finder Items and Copy Finder Items actions into the workflow area (in that order). Now select the Photos library and add the Rotate Images action to the workflow. Create a new folder on the desktop and call it Rotated Images. Drag that folder to the Copy Finder Items pop-up menu. In the Rotate Images action, choose the kind of rotation you want the workflow to perform—left, right, or 180 degrees. Save the workflow (File > Save) and give it an intuitive name such as Rotate.

Launch System Preferences, choose the Keyboard preference, click the Keyboard Shortcuts tab, select Services from the pane on the left, and scroll the right pane to the bottom of the list where you’ll find your Rotate service. Click the Add Shortcut button and press the keyboard shortcut you’d like to use to run the workflow.
Now, when you need to rotate an image, just select it and press this shortcut. The resulting image will appear in the Rotated Images folder you created.
Convert images to black and white

Sometimes black and white images are more appropriate for the project you’re working with. They’re easy to create with Automator—easier still because this workflow is almost exactly like the one I just described. Do everything I outlined in the previous workflow with these exceptions.
The folder you create on the desktop should have a more appropriate name—Black & White, for example. Remove the third action from the last workflow (the Rotate Images action). In Automator select the Photos library and drag into the workflow the Apply Quartz Composition Filter to Image Files action. From its list of effects choose Black and White. As with the previous action, assign a keyboard shortcut to it. Done.
This action has many options other than Black and White. Explore the menu and you may find some other possibilities that intrigue you.
If you intend to convert a lot of images, you’re better off creating this workflow as an application and then saving it to the desktop. When you need to perform your conversion, just drag your images (or a folder that contains them) to this workflow application.
Convert audio files
Your goal in this workflow is to convert an audio file to the iTunes Plus format (256kbps AAC) and add it to your iTunes library. You might do this if you have a lot of uncompressed audio files (say in WAVE or AIFF format) that you’d like to make smaller.
This one is best employed as an application, so you can drop files onto it for conversion. Select File > New in Automator and choose Application in the template chooser. Click Choose.
From the Music library, drag the Encode to MPEG Audio action into the workflow. Additionally add the Import Files into iTunes action. From the first action’s Setting menu choose iTunes Plus. Configure the menus in the second action to read Existing Playlist Library. Create a new folder on the desktop and call it Converted audio. Drag this into the Destination pop-up menu in the first action.

Save the workflow as an application and place it on your desktop. When you want to convert a file and add it to iTunes, just drag it on top of this application.
Note: If you’re not interested in adding the file to iTunes, you can accomplish the rest of it without Automator. Just select your audio file and choose Finder > Services > Encode Selected Audio Files. An Encode to MPEG Audio window will appear where you can choose from four settings in the Encoder pop-up menu—High-Quality (128kbps AAC), iTunes Plus (256kbps AAC), Apple Lossless (no compression applied), and Spoken Podcast (ABR 22.05 Khz AAC).
Convert movie files
Gee, converting audio files seems so easy that doing the same with movies should be a snap too, right? It is.
As with audio files, you can skip Automator altogether if you just want to convert your QuickTime movie files. Select the video you want to convert and then choose Services > Encode Selected Video Files from the Finder menu. (You will not see this option in the Services menu unless you’ve selected a video.)
An Encode Media window appears from which you can choose from among five settings—480p, 720p, 1080p, Audio Only, and Apple ProRes. In the case of 480p and 720p, you have the option to choose Greater Compatibility or Higher Quality. Greater Compatibility means the files work on more devices (old-style video iPods, for example). Higher Quality means the files won’t be compatible with those older iPods and will be larger (and, of course, they’ll look better on these devices than those encoded at the lesser setting).
Where Automator can be helpful is in adding your converted movies to iTunes. You do this just as you did in the previous workflow—add the Import Files into iTunes action. In this instance you’ll want to configure its pop-up menus to read Existing Playlist Movies.
And there’s more
These are very basic workflows for performing common tweaks. If your needs are greater—you want to take these images and upload them to a server, plant them in documents, or share them with others—there’s a good chance Automator can provide a way.