One of the easiest ways to find images :
Google Image Search
http://images.google.com
But be careful... these images are not necessarily free. You should check the wegb site where the image is found to see what the restrictions might be.

My favorite site for Background Texture Images and Clipart:
GRSites.com
http://www.grsites.com/
This is a great site, with a huge collection of backgrounds, as well as clip art. With the backgrounds you can even modify their color and brightness right in youur web browser.

The Whole Internet Guide to Clipart
http://www.Best-of-Web.com/computer/clipart_index.shtml
This is a HUGE starting point, and it leads to thousands of images

ClipArt Connection
http://www.clipartconnection.com
Another large collection, with a good search feature.

Clipart by the Wizard of Draws
http://www.wizardofdraws.com/main/thelist.html
This is a great site, with a large collection of original cartoon-like images.

Barry's Clipart Server
http://www.barrysclipart.com

ANIMATED GIF COLLECTIONS

Animated Gif Finder
http://www.gifs.net/animate/giflist.htm
This is a HUGE list of animated gifs. Use your browser's "find" function to search through this page.

Animation Attic
http://www.animationattic.com

Animation Factory
http://www.animfactory.com

ClipArt Connection Animation
http://www.clipartconnection.com/animations

Animation Library
http://www.animationlibrary.com/

ClipArt Warehouse - Animations
http://www.clipart.co.uk/html/anim.shtml

SITES FOR CONSTRUCTING TEXT IMAGES
These sites allows you to MAKE your own banners, animated images, etc.

FlamingText.com
http://www.flamingtext.com
Highly recommended!

CoolText.com
http://www.cooltext.com

MediaBuilder
http://www.mediabuilder.com

SITES FOR ONLINE IMAGE-EDITING
These sites allow you to upload images and perform basic editing functions. Very nice when you don't have access to image-editing software. Perhaps the most useful function is making transparencies in your GIF images.

Gifworks
http://www.gifworks.com
This one allows you to edit GIF images only. You can even edit Animated GIFs!

Myimager
http://www.myimager.com
This one allows you to work with both JPEG or GIF images (you can convert between these formats).