The Adium homepage has some issiues lately, eg the 1.0 Beta page cannot be reached. If you want to download the latest beta, it's here: http://adiumx.cachefly.net/Adium_1.0b14.dmg

Keep in mind that it's not considered stable and regular users are advised to use 0.89.1, but IMHO this 1.0 Beta is way better.