Convergence.NET
The most annoying thing about alternating between two operating systems is maintaining two identities. Settings, bookmarks, files, email, etc. must all be kept in duplicate, triplicate, or worse. The ideal solution to this information multiplication would be sharing this information (call it your profile) across all operating systems and devices. As mentioned on Slashdot, this really isn’t anything new. However, I think the idea has been left to gather dust for too long. Microsoft has resurrected it as part of .NET, but who the hell would trust MS to do this right? I think the old Netscape 4 version was a better start. In my mind, one could setup a server, possibly as an Apache mod, or as a standalone server, to which clients of all kinds (browsers, email, etc.) could connect and synchronize information. Certain systems do this already (yahoo, hotsync, intellisync) but the chain is usually pretty limited. Apple seems to be moving in this direction with OS X, iCal, iSync, and the iPod but that’s just one platform. This kind of thing should be pretty easy to implement on any platform using existing technology (LDAP, Kerberos, SSL, WebDAV, etc.) but simply hasn’t been.