It's always been possible to get Linux desktops to work on Windows-based networks. I do it all the time. But, it's not a job for an average Linux user or a Windows network administrator's whose MCSE (Microsoft Certified Systems Engineer) certification still has wet-ink. Now, though, Canonical, Ubuntu parent company, is partnering with Likewise Software to make it easier.
Likewise is the creator of Likewise Open. This is an open-source program that lets Linux and Mac users authenticate against and join Active Directory domains and forests. It also enforces AD (Active Directory) password policies across Linux systems.