The Android has some Microsoft Exchange support; how good it is depends on the vendor.

I was at a PDA software presentation the other day, and the vendor mentioned the problems of integrating the different Android handsets with their products.  I asked if it was because of the different operating system versions (Cupcake, Donut, Éclair) out in the market.

No, it’s because there are several different Exchange ActiveSync clients, some are better than others.  Another thing to note, if the Android handset has “Powered by Google” stamped on it, it means there is no Exchange ActiveSync client installed.  You have to go and download one.

If I owned an Android phone, I would buy the DataViz RoadSync application.  DataViz has been working in the handheld device market since 1984, and are a Microsoft Gold partner.  And they make the Documents To Go product, which I can recommend highly.