OmniFocus provides several ways to sync your data between devices, including MobileMe and their beta Omni Sync Server. If you have a web hosting account (such as DreamHost) that supports WebDAV, you can set up your own sync server without having to subscribe to any other services. Here’s how I set it up on DreamHost.
1. On your web host, set up a WebDAV directory. On DreamHost, go to Goodies -> Htaccess/WebDAV and choose a fully hosted domain. In the next screen, enter the name of a directory you want to use for WebDAV and password protect it.
2. In OmniFocus on your Mac, go to Sync settings and switch to the advanced tab. Enter the name of a subfolder inside the directory you specified in step 1.
3. Enter that same path on all of your mobile devices that you want to sync with it.
I find it to be much faster than MobileMe using my DreamHost server. Your results may vary depending on your web host or server.