I discovered a while back that you can tie together your Basecamp, Highrise, and Backpack accounts with one login if you use your OpenID account. When you log in with your OpenID, there will be a bar across the top of your accounts with links that let you switch from one to the other easily. What I did not know was that you can also link your different Basecamp accounts together with your OpenID. I discovered this today when I set up my PodCamp San Antonio login on Basecamp to use my OpenID.
This is great because it means that you can have a free account for your own personal project and have additional projects through other people’s accounts. So long as you use OpenID logins in your guest accounts, you can have a network of interlinked accounts under a single user name and password. How awesome is that?