This is exactly what Bugmenot is made for. You can search per url and the site will give you logins (if there are any) for that website. Of course you can also submit your dummy accounts to this site so other people can use.

Even better is the fact that for all the Firefox users there is an Bugmenot Extension which is really easy to use.
You just right click on an login form and then select “Login with Bugmenot” and the extension automatically looks for login data on the bugmenot website.
And if an account doesn’t work the extension will try out the next account until you are logged in or until there are no more accounts. This site and the extension saved me allot of hassle on different occasions, and hopefully it will also be the same for you.

I found a nice search engine that lets you enter a website of your liking and displays login data for the website, if they have it in their database, that is. If you enter nytimes.com for example the search reveals one login for the site and this one is actually working.

Its a great site that probably has not logins for all sites on the internet but the most common ones, if you want to try it out go to Bug me Not

Bug Me Not basically offers a database of semi-public logins for many different Internet services. Just enter the url or name of the site you need a login for, and Bug Me Not will display all hits to you afterwards.

It happens that not all of the logins work which is only natural, considering that site owners can use the search engine as well to block the public logins on their sites. Users have options to confirm that links are working, and the percentages are shown next to the logins one site.

Every user of the site can vote, you do not have to be logged in or a registered user to do just that. Bug Me Not is a handy site for users who need a temporary login for a site to access specific data or contents.