Converting Desktops to Thin Clients?

tfiedler asks: "I manage about 3500 desktop computers and was recently asked by my CIO to begin looking into thin client computing, something like WYSE terminals. I'd like to know, what are some good functional, and more importantly, manageable options to convert existing desktop computers into what would essentially be a Citrix terminal? I was thinking some brand of Linux that starts up an X11 session, starts the Citrix client and connects to our server farm. The user would see a Windows logon, our apps would function as normal and I'd get the benefit of performing a LOT LESS client-side maintenance. Any suggestions?"