Trillian Astra, which has been in development for nearly three years, is now available to users as a public beta. You won't need to register for a private key to download it. Just go to the site and download.
For those of you who aren't familiar with Trillian, Trillian Astra is the next generation of Trillian, the popular multi-account instant messenger from Cerulean Studios. Astra is pretty. Really pretty. The new default skin called 'Cordonata' has that slick plastic look you'd find on Mac OS X or Windows Vista. It's also functional, taking up no more onscreen space than the current version of Trillian does. It is an all-around great option for chatting on multiple platforms so I encourage you to check it out.