In 37signals' internal Campfire chat room, Jamis said, "Highrise is great for aggregating information about all the accounts I have for various web applications."
For instance, I've got a Blinksale account to send invoices for the PeepCode ad on my blog. So, [in Highrise] I have "Blinksale" as a company and my login URL as a web address in the contact info for blinksale.
Since I only log into Blinksale once a month, there's no way I remember what my login url is or my username. Highrise is a good central place to manage that, especially since I can forward my "welcome" email from Blinksale to it (as well as record any Blinksale related tasks and other correspondence). I use the "About" field for recording my username and other info too.
So whenever Jamis pulls up his Blinksale page, his login URL is right there:
