What do I look for when shopping for a knife sharpening stone?
What are the different kinds; pros/cons of each?
Besides a kitchen supplies specialty store, where can I find one (and possibly accessories)?
How long does a stone last?
Approximate cost (USD)?
Care/Maintenance?
Anything else I'm missing?
Thanks.

Knife sharpening stones come in all shapes and sizes and can vary greatly in price. If you have more money than you know what to do with, you can purchase a verynice tri-stone knife sharpener, common in professional kitchens for about $220-230 USD; otherwise I'd suggest going to a hardware store rather than a gourmet kitchen store. Hardware stores, ie Lowes, Home Depot, etc. usually carry very cost effective stones for sharpening knives, axes, handtools, etc. I recently just purchased a stone and honing oil, for about $20.

In hardware stores, they're usually located around other hand tools/bits/hand accessories. Sharpening stones vary in degrees of coarseness, just like sandpaper. Look for a stone that's large enough to comfortably use. 10 inch is excellent, 8 and 6 inch are usable, but I wouldn't go any smaller. It's very diffeicult to get a fine, consistent edge on a 10 inch chef knife with a 4 inch stone. I'd suggest looking for one that had both a coarse and a fine side.

Look around the aisle to find the honing oil. The oil is important because it lubricates the stone which makes sharpening easier, more efficient, and helps to carry away shavings/debris. I'd recommend using this type of oil as opposed to a cooking oil, ie canola, vegetable, peanut, because cooking oils will clog the pores of the stone, rendering it ineffective. I know from experience.

Stones vary in maintenance and will have directions on the packaging. Properly cared for, sharpening stones should last years.

Hope this helps