When we had our first child, I couldn't find an online registry that I liked, so I scripted a rudimentary one up one night. It worked really well. My wife loved that she could register for intangibles like "Bring us dinner", or any gift from any store. When the baby was born, I took a lengthy paternity leave and, like you, thought I'd build a web app for others to use the registry. I actually took the idea to a local startup bootcamp and it was torn apart by the instructors/angels and left to die on the boardroom floor. Too hard to generate sufficient revenue. Here are a couple of tidbits from my experience for you:
1. One angel had invested in a universal registry and said it took them three years to find any revenue at all. What they did was pivot into a wedding registry that enabled guests to contribute to the couple's honeymoon fund. They made money on travel agent referrals to the couple.
2. This is a crowded market.
A lot of the comments in this thread (like mine!) note how great your site looks. When I showed my site to the bootcamp people, I emphasized my slick design. They essentially said, "No one gives a crap! What problem does it solve that isn't already solved by someone else!"
I thought, "But, but, but... everyone is like me right? Tech savvy and appreciative of good design and UX?"
Check out http://wishpot.com. They are a universal registry. All web 2.0 with social integration. They've got some funding (http://www.centernetworks.com/vc-funding-docstoc-wishpot-kaa...). Been around a few years now.
Here's a competitor: http://www.findgift.com/Services/Gift-Registry/. It was founded in 1997 by a couple from Georgia.
And another: http://myregistry.com. Second spot on Google for "gift registry".
Now check it out:
http://siteanalytics.compete.com/findgift.com+wishpot.com+my...
Good luck!