There are tons of ways to take photos of finished objects, and I'll try to get to all of them, but for now I'm focusing on small objects, like toys, hats, gloves, and even skeins of yarn for your stash page.
I didn't use Ravelry's stash feature for AGES, and when I did, it was a series of badly-taken webcam photos that didn't represent the yarn in any useful way:
Now, I take all of my small object photos using a curl or lightbox. This method results in photos that have a clean, white background with no "setting" in the shot.
To accomplish this look, you don't actually need any fancy equipment... A white sheet or piece of posterboard can make a curl. To start, just attach the material to a vertical plane (wall or chairback) and let the fabric or paper drape toward you, creating a gentle curve. If using posterboard, I tend to favor the matte side (the side that typically has the price sticker on it), so there's no reflectivity. Once you've created a curl, you have to determine your light sources.
Lighting can be approached many ways. Natural light obviously depends on the weather. Using the sun can be great (and cheap!) but the best results occur in the shade or on an overcast day, where you get all the ambient light of the sun with none of the harsh shadows.
I followed a tutorial and constructed my own little lightbox. I then went to Home Depot and bought two cheap worklights and two "daylight" bulbs. My final result was this:
Don't forget! Just a few more days to enter and win!