Microsoft Direct Gallery Live
http://dgl.microsoft.com
This is probably the best resources for images. Try here first before hunting elsewhere. Almost all the clipart images are scalable, which means you can change the size of the image without affecting the quality. There is a tutorial (click here) on how to use the site in conjunction with MS Word.
note: You have to use Internet Explorer to access this site properly.

English Conversation Illustrations
http://raq1.aminet.or.jp/~yasu/illustrations/index.htm
This is a collection of very nice illustrations for flashcards. It has images for wide range of different topics.

Google Image Search
http://www.google.com/imghp?hl=en&tab=wi&ie=ISO-8859-1&q=
Just type in a key word or words and let Google scour the net for images. Advanced search options let you define size of image, colors and file format.

Altavista Image Search
http://www.altavista.com/image/default
Like Google, but also has an option to search corbis.com for professional quality images (though they are quite small).
from: C. LeRoy Mobley

Clip Art for Foreign Language Instruction
http://www.sla.purdue.edu/fll/JapanProj/FLClipart/
A collection of gif images, covering verbs, adjectives and nouns.

DiscoverySchool.com
http://school.discovery.com/clipart/
A collection of gif images.

Clips Ahoy!
http://www.clipsahoy.com/
A collection of gif images, covering a variety of subjects, most in color.
note: click the links on the left hand side of the page in the Free Clipart Categories column.

Dr Jim's "Get Emotional"
http://www.jimcromwell.mcmail.com/emotions/Home.htm
A collection of simple iconic images of over sixty facial expressions indicating a variety of emotions and feelings.
from: C. LeRoy Mobley

Criss Cross
http://www.genkienglish.net/CrissCross.htm
A fun game that gets students participating.

Feel free to alter or take from any of the following for your lessons.

Introduction Lesson
https://cruinthe.tripod.com/L01-introduction.zip
Has some a question and listening comprehension sheet - will need to be altered as it is somewhat personalised.
from: Andrew Scott

Destinations
https://cruinthe.tripod.com/L02-destinations.zip
Has 14 Flag FCs (You'll need a color printer) and an A4 sheet with activities you might do in each of those countries.
from: Andrew Scott

Packing
https://cruinthe.tripod.com/L03-packing.zip
FCs (B&W) for 24 items you might take on holiday (or not) and an A4 sheet with some activities.
from: Andrew Scott

At the Airport
https://cruinthe.tripod.com/L04-introduction.zip
Directions, Prepositions and Places at an international Airport. Maps and activity sheets.
from: Andrew Scott

ELT Web
http://www.eltweb.com/liason/
A large index of links to useful resources.

Dave's ESL Cafe
http://www.eslcafe.com/
A useful resource, check out the Idea Cookbook.

ESL Point
http://www.eslpoint.com/
Has a huge selection of links to ESL sites all over the net.
from: C. LeRoy Mobley

edHelper.com
http://edhelper.com/
Has utilities to design puzzles like wordfinds, and crosswords.
from: Desiree

Karin's ESL PartyLand
http://eslpartyland.com/
Provides Lesson Plans, Ideas and Links.

ManyThings.org
http://www.manythings.org/
Mainly for ESL Students, but it has some good ideas and a page of over 700 English Signs.

Developing Teachers.com
http://developingteachers.com/
Nice looking site. Has a large selection of lesson plans.

The Internet TESL Journal (For ESL/EFL Teachers)
http://iteslj.org/
An ESL Journal you can subsribe too. The Things for ESL/EFL Teachers page has things like jokes, activities, lesson plans and teaching techniques. Also there is an excellent collection of questions covering a wide range of topics.

EverythingESL.net
http://www.everythingesl.net/
Featuring 54 lesson plans, 35 teaching tips, 185 downloadable classroom activities, and 57 resource picks. Has some interesting ideas, though many of the lesson plans require additional resources (books).

English-Zone.Com
http://www.english-zone.com/
Covers many different areas, however many of the resources require you to become a member (US$20/year). That said they offer quite a few free resources too.