Another option is to have your children make gifts for their siblings. This is usually less expensive, and the children are putting something of themselves into their gift. Craft stores are beginning to stock more and more craft projects that are specifically for kids to do.
For example, candle-making has become a much easier and safer craft with the advent of special, pourable wax crystals. The wax comes in a bag and looks like candle "dust." You simply pour layers of the different-colored crystals into a clear jar and add a wick. It requires neither boiling wax nor heated surfaces.
Plaster of Paris crafts have become easier with the advent of "Faster Plaster." These kits come with all sorts of molds, which can be quickly made into ornaments or toys and then painted.
Beads are popular again, and you can find lots of kits for making homemade jewelry. A special type of bead called "Perler Beads" come with a template covered with little plastic posts. You set the beads down on the posts following the design of the template, then run a hot iron over it. The beads melt just slightly, making a permanent shape from the template.
There are lots of special kits - made just for kids - for making barrettes, glitter art, sand painting, finger puppets and pendants. Kids can use rubber stamps and colored pencils to make customized stationary or stickers for their siblings.
Encourage your kids to use their imaginations to make custom-made presents, too. If a little brother collects Matchbox cars, make a special garage for those cars with a shoebox, some cardboard and a little contact paper. If a sister collects stickers, make a special sticker book by covering construction paper with clear contact paper. Make a locket with a secret compartment by covering an empty matchbox with a construction paper or craft foam design and stringing a ribbon through it.