Project of the day: OpenID for Java.net
I wrote and deployed an OpenID provider service for java.net users.
For those who are new to OpenIDs, this service allows java.net users to log in to other sites by using the java.net ID as the identity (for example, try Stack Overflow.) This eliminates the need to maintain separate passwords for each site, among other things.
That said, the primary use case of this service is not to become just one more OpenID providers — between Google, Yahoo, AOL, and Facebook (to name a few), people are already likely to have multiple OpenIDs.
The real motivation of this service is to host "peripheral" systems and services on top of those that are provided by java.net. For example, if you want to run your own JIRA, JIVE forum, Trac, or Wiki for your project, it'll be more convenient if those services delegate authentication to java.net. In this way, you can correlate users on those peripheral systems to the users on java.net. This also allows you to perform authorization based on their project roles (for example, you can only allow certain operations to committers of your project.)
Update: the service is now moved to the openid.java.net domain for more authenticity.