A silver anniversary means twenty fifth anniversary gifts! Why not make it homemade?
For a twenty fifth anniversary gift what about getting some pictures of the couple from their wedding day up until the present? Use a computer to make a slide show with the pictures. You can burn it all to a CD and make copies for the couple and their party guests. While at the party you could even play the CD for them and the couple's guests. If you aren't good with a computer find someone who owes you a favor :0) Have them help you.
Or you could make a scrap book with the couple's pictures in it and all the mile stones they have gone through. Their wedding, having children, buying a house, etc...
You could make a gift basket of all the couple's favorite things and put it in a silver metal bucket you can find at a hardware store. Wrap it all up with a big silver bow.
If you really want to get crafty, you can create a wind chime using silverware. Go to your local thrift store and find some interesting silverware. The cool thing is that nothing has to match! You can bend and twist forks, spoons and knives using simple tools like pliers and a hammer. Use thin silver chain to hang the pieces from a spoon bent into a circle.
Plan a surprise trip for you and your honey. After twenty five years of bliss a spur of the moment trip might be the greatest gift ever. Time to relax and just get away! Hop on a plane and go to Vegas. What better place to spend some silver:0) Take a trip to an exotic Caribbean Island.