Automator seems to be one of those unknown or ignored Apple-made apps.  But it is very powerful and can save you a lot of time.  It has also been part of OS X for a long time.

Purpose

To save time by automatically scaling down images (while keeping the original file) to a pre-set size as opposed to manually editing each one.

Requirements For This Walkthrough

Materials

1. Mac with OS X
2. Large image files

Downloads

1. Automator workflow

Knowledge, Skills, and Abilities

• Ability to navigate throughout a computer OS
• Knowledge of basic computer terminology

Step-by-step Instructions

Create the Automator Workflow

You can also download a a pre-built workflow.

1. Create a folder for the scaled-down images to go

2. Open /Applications/Automator

3. Create a workflow similar to the following: (editing the folder and size fields)

4. Click File > Save

5. Save as something like Reduce to 800×600

Use The New Contextual Service

1. Right-click a large image file

2. Click Reduce to 800×600

3. Watch the magic happen

The scaled-down image will now be revealed in the folder you designated.  The original remains in-tact.  This operation can also be completed on many files at once.  In this example, the picture was 1.8MB and was reduced to 144K.