You did not specify which platform you are using (Palm, Pocket PC, other), so I can't be to specific in terms of solutions. However, there are a number of ways to synchronize e-mail, calendar, scheduling and other personal information management information. For example, you can use your cell phone to dial into your remote computer and link your systems for a synchronized data refresh. This is one option offered as a standard feature on the Palm platform, and as an option through third-party service like AvantGo. If your handheld has built-in wireless (802.11 and/or Bluetooth), you might be able to link mobile systems or connect remotely to your host system or server. Bluetooth, in fact, is great for swapping data and PIM info between mobile devices.
If you have a communications-centric device, like the Palm Tungsten/W or new Treo 600, you can usually synchronize information through your wireless carrier. For example, AT&T Wireless offers Office Online, which allows synchronization for Microsoft Outlook and Lotus Notes platforms.
You can also use a number of third-party software programs and environments to set up synchronization areas, allow authorized access, and select which files can be accessed by which people. One of these is LapLink Gold and the LapLink EveryWhere software available from LapLink, Inc.. This software let's you connect and access the information contained on remote devices to share needed data and files. You can also use it to take control of remote systems, operating applications and coordinating functions from a distance.