I had the same question about a year ago and after trying out a few gift sites, settled on giftster.com.
It provides everything the amazon wishlist did, but allows you to add items from anywhere on the internet without a fuss. It works well enough that I was able to convince my entire family to move to it, which is a real victory.
Grunka Lunka dunkity doo We’ve got a friendly warning for you Grunka Lunka dunkity dasis The secret of Slurm’s on a need-to-know basis