Suggestion#1: Know how big your images are! Windows: right-click and choose "Properties." Mac: right-click or ctrl-click and choose "Get Info" or simply select the file and use CMD-I. Sizes are in KB or MB (=1000KB). Emailing anything larger than 3MB is not recommended, and 500KB or less is good for inserting images into documents or web pages.
Suggestion #2: If you only intend to use your images on the computer (in documents, on the web or in presentations) I recommend turning the resolution DOWN to 3.2Mpx. This still gives you a decent quality image (will still print fine in 8x10) with a manageable file size. True: Zooming in to choose just a small portion of your picture will result in degraded quality.
Suggestion #3: Learn how to resize your images.
Windows: Our school computers have the "Image Resizer Powertool" installed. This is a free tool available from Microsoft (Google it for the link). Once installed, you can right-click on an image and choose "Resize Pictures," then choose from a list of sizes (small, medium, large). This will create a COPY of your image with the size added to the filename. You can also select multiple images and resize them all at once.
Mac: The Preview program has the capability to reduce the quality of images. Open the file and choose "Save As," then rename the file (so the original is preserved) and move the quality slider to the left. Unfortunately this only works for single images.