All the following links take you to over 900 samples of clip-art which is in PC wmf ( Windows Metafile Format - a vector based format good for Microsoft Word and Powerpoint. You should be able to scale these up or down without the losses in quality associated with GIF and JPEG bit-image formats.

Right mouse click on the graphic you want then Copy. You can Paste the figure straight into Word.

Animals  
Cars
Chemistry Apparatus - Basic, Beakers
Electrical - Circuits, Miscellany, Switches, Symbols, Unilab Simple Electricity
Lego - Car, Castle, Figures, Space, House - Bricks, Doors & Windows
Minibeasts - Beetles, Ladybirds & Water bugs
Miscellaneous
People - Blobbies, Bones, Dummies, Faces, Miscellany, Organs, Outlines & Skeleton
Plants - Flowers, Fruits & Miscellany
Signs - Ear, Equipment, Eye, Hand & Head Protection, Hazards, Hazardous Chemicals, No-Smoking & Safety
Technology - Fanfaces, Fans, Fixings - Nails & Screws, Linkages & Projects

See also Gander Academy's - Clipart for Students and Teachers - loads of links to clipart sources
Have a look at Fife Education's Image Bank for some nice hand-drawn images (44 thus far)

See Becta - Science Clipart

Science Photo Library - A great site for science images - register for free to search for what you want from over 100,000 images.

or try the Microsoft Site or LTS Royalty Free illustrations    Early years -