What is the best way to make photographic slides of paintings?
babygrrl, I assume you mean photographic slides. I've done these for some artists I know. If you are using standard slides get a good 35mm SLR camera, and a heavy tripod. My favorite film for this purpose is Fuji Velvia. Hang the canvas on a wall then position your camera and tripod to fill the frame. For paintings I like to use 2 flashes on each side pointing in at 45 degrees. Use the timer on the camera to minimise vibration. My favorite lens for photographing paintings is a 55m macro lens. It is true that I'm not shooting in the macro range but my macro lens is the sharpest lens I own even at infinity. A standard 50mm prime lens will work very well. Adjust shutter speed so you can shoot at your lens' best aperature. If you don't know its best aperature than try a mid aperature like f/5.6.
If you need superslides than do the same basic thing with a 120 roll film camera. I have an old Koni-Omega that looks like it has been through wars but still takes great pictures.
Now that digital photography is so popular film SLRs and even medium format cameras are getting to be great deals.
Taking pics of the paintings with a digital and place them on your computer. There are tons of free programs you can use to make slides. The one that comes to mind is a free one called Picasa 2.