Seek and Find Bags or I Spy Bags are such an awesome toy! I love search for little items to fill them with, especially things that are out of the ordinary! To make one, you will need:
2 - 6.5x6.5 inch fabric squares
1 - piece of clear vinyl about 4inches square
20 or so little items
a small piece of paper listing the items- you can laminate this with contact paper or a home laminator to make it last longer, punch a hole in one end
a small piece of ribbon
half a cup or so of filler To Find the Items:
Look for little things all around you- you can use ordinary things like nuts or bolts, coins, pencil erasers or paper clips. You can also try finding other fun things like shaped buttons, or shaped erasers, doll house accessories, jewelry charms or game pieces.

For Filler:
In my opinion the best filler is poly pellets. You can find these in any craft store. You can also use rice and I've heard of some people even using dried beans.

To Make the Bag:
Take your top square and fold it diagonally and mark 2 inches diagonally from the outside corner. Cut from this mark toward the folded edge of the square. Fold diagonally the other direction and repeat. You should have an X cut in the center of your square. With the right side down, fold the flaps of the X toward the outside and iron. Trim the corners off of the flaps. Layer the vinyl square under the wrong side of the square. Sew them together along the edges of the opening with a 1/8inch seam allowance. Trim the vinyl to about 1/4 inch around the edge of the opening. Round the corners. Thread the ribbon through the hole in the list of items. Fold the ribbon in half and lay it on the back square, raw edges together and toward the outside of the square. The ribbon should only be about one inch inside the square. Pin in place. Layer the square with the window on top with right side down. Sew the squares together with a 1/4 inch seam allowance. Leave one edge partially open. Zig zag stitch along the edges to keep them from fraying. Clip corners and turn right side out. First put in your i spy items. Then add about 1/2 or 3/4 cup of filler. I used a canning funnel so I didn't spill the pellets all over the place. I recommend using a measuring cup to scoop the pellets because they will stick to your hand and then fall off all over the place.

You only want the bag to be about half full or it will be hard to look for the items in the bag. Fold the open edge in and pin closed. Sew the open edge closed with a 1/8 inch seam allowance. Make sure that the poly pellets are out of the way and that you catch all the edges. And you're done! Have fun searching!!

P.S. Make sure you take any safety precautions that are necessary to keep kids safe from the small objects in this toy, including keeping away from children who are under 3 or still mouth things. I'm not responsible for your actions, so please remember that you are!