Most people have an Amazon wish list. Pretty cool way of letting others know what you would like for a birthday, Christmas etc. It is also pretty handy to remind yourself of things you'd like to buy, but without the financial disaster of buying it when you find it.
The biggest problem has always been that there is a lot of stuff you'd like that you can't get from Amazon. Well, they've addressed that problem with their 'universal wish list' feature.
Adding the favorite is easy. Create a wish list in Amazon, then on the left side look for the 'universal wish list' link and follow the directions.
For example, Fox Mustang Restoration doesn't have a wish list feature. So I navigate to the page of the item I would like for the Capri, select the 'Add to Wish List' favorite in Firefox. Amazon then displays a popup for you to pick the picture of the item, change the description and add the price. Hit 'save' and then 'save' again on the Amazon page and your item is added to the wish list.
Buying from the wish list is a little more difficult, but not much. When your friend buys something, the select the 'Shop This Store' button on the wish list, then submit their email address so the item can be marked as 'bought'. So no duplicates.
I actually think Amazon missed the UI on this. What they should have done was opened the link in an iFrame, and put a 'yes I bought this' link in a toolbar above the linked-to page.