Someone came up with a completely brilliant idea: make stickers of everything that's hidden! When you find that pencil or book or golf club, you put a sticker over it. This makes the whole process a lot more fun for really small kids like mine. My five-year-old is a little past them (he rarely needs help finding anything), but it wouldn't be fair for the 2 1/2-year-old to have all the sticker fun, so we're sharing. She can find about a third of the hidden objects, and then I give her hints for the rest.
We also got a set of the regular Hidden Pictures, which I'm keeping until we've finished the sticker set. The advantage of those, of course, is that you can do them over and over because there are no stickers showing where everything is. But they're harder, so we may hold off on them for a little while, or do them together a little at a time.
You can buy both sets here on the Highlights website, along with other sets. These are great for encouraging attention to detail, the idea of perspective, and pattern recognition. And they supposedly help develop depth perception.