Open Source PDA Sync Servers?

bandix asks: "There's been quite a buzz going on slashdot lately about various linux based PDAs. What we haven't heard too much about is the software available on the client side. Sure there are plenty of workstation hotsync clients, but what about the web-based stuff? One of the coolest ideas I've seen in a while is the AvantGo.com service that allows PDA users to MAL-sync their data up to an AvantGo server. AvantGo has released the source to an malsync client at mobilelink.org. But where is the web-based calendar software that supports syncing with it? Where do I get the software to setup my own open source AvantGo.com-like service? That application is just as useful, if not moreso, than actually running a flavor of Unix on the PDA. Anyone out there working on a solution or know of one hidden away somewhere?"