Go green and check out this site of fabulous antique rings:
There are countless sites similar to this one, but this one looked really neat.
I love the idea of having a ring that is 80-100 years old. Now that is some history! I also love it when a guy uses a ring that is already in the family. You can have it re-set, add stones to it, or present it as is. I can't think of anything more special.
If you do decide to buy a new ring, please make sure that it is a conflict-free diamond. The concept of a "blood diamond" is unfortunately a very real thing, not some scheme Hollywood devised to sell movie tickets. Having traveled to Africa twice, I can assure you it is a reality for many people who are forced to work in this industry under horrific conditions.
For more information on conflict-free diamonds, go to www.groomgroove.com/our_pick/conflict_free_engagement_rings.php.