ShouldDoThis.com is the site I wish I had thought of. It allows anyone to submit a suggestion for anything, then the user community can vote on the suggestions. To submit an idea you need a user account, which takes about 5 seconds to create. From there, all you have to do is type in who the suggestion is for, and what the suggestion is. When you find an suggestion you like, you can click the "Should do this" button and it adds you to the list of supporters, you can also write an entry giving your two cents on the suggestion. You can easily search suggestions, and view all the suggestions for a particular entity, which actually gets it's own subdomain like http://google.shoulddothis.com/. The site is attractive, easy to use and the developers are incredibly responsive to user suggestions (go fig). If you like this website, I strongly recommend checking out Should Do This.
I love the spirit of "Should Do This." It enables regular people to submit ideas for the things they care about and raise some awareness for them. The site also reinforces the idea that people generally want the products and services they use to be better and are willing to try to help out. The site also exposes how perceptive customers are. Companies should look to "Should Do This" as a way to crowd-source product development, spot trends, and predict customer expectations. Currently, I think Should Do This is a really untapped resource on the web. For instance Engadget frequently has entries in the style of "How would you change _____", and the commenters just go crazy. I'd love to see Engadget and other websites use Should Do This to manage user suggestions.
One thing "Should Do This" does that I have very mixed feelings about is it rarely lists suggestions or users in any kind of hierarchical order. You can't see a ranked list of users, or all ideas. Suggestion featured on the home page are just the ones with the most recent activity, not the most votes. Only on a particular entity's page are suggestions ordered by votes. While I really like that these measures keeps the site from being exploited by a hyperactive minority or becoming overly competitive and I also feel that its may have stifled activity to some degree. I think the site could become a better vehicle for actually causing change if top ideas were featured on the homepage, making them easier to see at a glance. I think the intention is that the an individual entity's page is really a better place to view top ideas, but something about the layout of that screen doesn't quite have the impact you might want: the suggestion titles are a little small, and the user icons are distracting.
The content on Should Do This is really great. There's almost no spam and the suggestions are very earnest. It's very different from HalfBakery.com which is a great source for hilarious ideas that no one really expects to come to fruition. However, I'm really worried that could one day change, especially because currently there really isn't a quick way to mark something as junk. My biggest disappointment is Should Do This users don't always explain their ideas thoroughly. Also, while the user community is growing, it's still not as active as I'd like. For instance the top ideas on the site seem to have about 40 votes.