I built something. It's called Wish List Granted.
It's a mash-up using Amazon.com's Wish List functionality. What you do is you hook up your Amazon wish list onto wishlistgranted.com and pick one item. Then you share that page with friends and familiy and they can then contribute a small amount each. When the full amount is reached, Wish List Granted will purchase the item and send it to you.
The Rules page has more details if you're interested.
The problem it tries to solve is that you have friends would want something and even if it's a good friend you might be hesitant to spend $50 on a gift to them. I'm sure you can afford it but if you have many friends it gets unpractical. However, spending $5 is another matter. Hopefully Wish List Granted solves that problem.
Wish List Granted started as one of those insomnia late-night project. I first wrote a scraper using pyQuery then a couple of Django models and views and then tied it up by integrating Balanced Payments. It was actually working on the first night. Flawed but working start to finish.
When it all started, I used Persona to require people to authenticate to set up a Wish List. After some thought I decided to ditch that and use "email authentication" meaning they have to enter an email address and click a secure link I send to them.
One thing I'm very proud of about Wish List Granted is that it does NOT store any passwords, any credit cards or any personal shipping addresses. Despite being so totally void of personal data I thought it'd look nicer if the whole site is on HTTPS.
More information on the Help & Frequently Asked Questions page.
UPDATE
Wish List Granted is now shut down. Sad.
Comments
As someone who works on Persona, I'd be interested to hear why you decided to ditch Persona!
If I had to have any authentication, it'd be Persona. In fact, that's what I use for the admin dashboard.
To a complete strange with attention span nearing 0 seconds, not having to do any authentication is a win.
Did you publish your code for this project anywhere? I'm curious to see how you tied it all together.
Not yet. Will do at some point.